The Collaborative on Oceanography and Chemical Analysis (COCA) and suggestions for future instrumental analysis methods in chemical oceanography

COCA Working Group*1 *Corresponding author Chris Measures, Department of Oceanography, University of Hawaii, 1000 Pope Road, Honolulu, HI, 96822, USA. Tel +1 808-956-8693 Email: measures@hawaii.edu 1 The members of the COCA Working group are listed in Appendix I Submitted to a special issue of Marine Chemistry June, 2014.

Abstract

The ability to make measurements accurately and precisely is the sine qua non of chemical oceanography. The development of theory and its transformation into modeling is completely dependant on the understanding gained through accurate measurements of oceanic properties. Chemical oceanographers, by making measurements of various chemical elements in ocean water, seek to discover, understand, and quantify ocean processes and use them in conjunction with other branches of oceanography to understand how the oceans interact with Earth system processes. We use this information to understand how the planetary biogeochemical systems affect and interact with the climate and use the chemical record in the sediments to understand how these systems operated in the past. With this knowledge we can build accurate models to predict responses to future climate forcing events. The primary inputs to chemical oceanography are dominantly provided by applied analytical chemistry.

The construction of large networked observing systems and the development

of a variety of autonomous vehicles have provided an unprecedented opportunity to study the ocean at spatial and temporal scales that have not been previously available to the ocean research community. However, as a result of power availability, mass and size constraints, and the limited ability to service instruments on these platforms, there are only a few parameters of interest to chemical oceanographers that can take advantage of this expensive infrastructure.

There is thus an urgent need to develop new methodologies in oceanography that can meet these constraints on the development and deployment of new sensors, and a need to catalyze interactions among chemical oceanographers, analytical chemists, and ocean engineers to bring new technologies into use for ocean sensors.

Analytical chemistry at this time is one of the most rapidly evolving areas; as a result it is difficult if not impossible for chemical oceanographers to remain cognizant of fundamental improvements in the field of analytical chemistry that could be profitably adapted for use in oceanography. This need to bridge the gap between chemical oceanographers and analytical chemists has been recognized for a long time (Goldberg, 1988) and past suggestions to improve the measurement of carbon system parameters (among others), Walt and Urban, 1995; NRC, 1993, have produced tangible results. However, in rapidly changing fields the connection between the fields needs to be reinforced at regular intervals or, preferably, on a semi-continuous basis.

This manuscript summarises a meeting that was held at the Department of Oceanography, University of Hawaii, March 26-29, 2013. The purpose of the meeting was to bring together chemical oceanographers and analytical chemists to

explore new developments in analytical chemistry that might be developed for use in oceanography. This manuscript has been condensed from the text provided by the attendees who are listed in Appendix 1. It is important to realize that this summary reflects all of those ideas, it does not therefore represent a consensus view. The plenary talks and the full text of the working group reports, and their members, are available on line at the workshop web site: http://www.soest.hawaii.edu/oceanography/faculty/chrism/COCA/Home.html 1. The rationale driving oceanographic chemical analyses.

Chemical Oceanography aims to quantitatively account for distributions of elements and molecules in the ocean by determining their external sources and sinks, their internal fluxes, and their internal chemical and biological interactions. By making measurements of chemical elements, molecules, and stable and radioactive isotopes in the ocean, chemical oceanographers seek to discover, understand, and quantify ocean processes and use them in conjunction with other branches of oceanography to understand the role of the ocean in the Earth System. We use this information to understand how planetary biogeochemical systems affect and respond to climate. Some of these properties actively affect the global climate system (e.g. carbon and its related properties such as nutrients), while others serve as paleoclimate proxies that help assess processes that have caused past climate changes. This effort must take into account the physical circulation of the ocean as a major factor impacting chemical distributions, as ocean currents and mixing moves water from reactive boundaries (air-sea, sediment-water, light-dark, submarine volcanic centers) into the interior. Dissolved constituents interact with the sinking particulate flux to move constituents downwards and remove many substances into sediments. This knowledge can be used to understand chemical records contained in oceanic sediments that reflect past changes in ocean circulation and processes and also to construct mathematical models that can be used to predict oceanic responses to evolving climate forcing.

To achieve this knowledge, oceanographers need to develop extensive data-bases for a variety of critical chemical species that have been found to trace important oceanographic processes. The types of data needed vary considerably ranging from high-resolution temporal and spatial sampling in regions with strong chemical and biological gradients and rapid water flows to relatively low sampling rates in more quiescent open ocean regions with weak gradients. In addition temporal records are needed from fixed sampling systems (moorings) as well as from autonomous programmed (sea gliders) or free drifting (floats) vehicles that can sample unattended for long time periods as well as operate in hostile environments and inaccessible regions.

Chemical concentrations in the ocean range from ~0.6 M for the major ions of NaCl down to femtomolar or lower for some short lived radioactive species. Every naturally occurring element is present in seawater, as are most of those produced by radioactive decay. These materials can occur in multiple oxidation states and can be associated with a variety of complexing ligands both organic and inorganic. Thus analytical methodology is challenged not only by exceedingly low abundances, but also by the presence of virtually every other element including neighbouring periodic table group members with similar reactivities. In addition many of the analytes of interest that occur at the lowest concentrations in the ocean are commonly used in manufactured materials or mobilised in large amounts in human activities so that contamination of natural concentrations by anthropogenic sources including those associated with water samplers and sampling platforms is a major obstacle. Thus oceanography requires a variety of analytical methodological approaches to making these measurements and depending on the problem being approached these methodologies have a variety of constraints. For example large-scale expedition style ship-based sampling where water sampling from the surface to the bottom of the ocean is repeated at intervals of 30-60 km needs relatively rapid shipboard analysis (8-10 samples/hr), but has little constraints in terms of power requirements. For sensors that can be attached to the packages deployed from ships sampling rates of several Hz are needed and the detection system must be able to function at pressures up to 600 atmospheres.

For autonomous sampling devices, such as sea gliders and Argo floats, that have relatively slow translation speeds the main constraint is the availability of electrical power, but the stability of the instrument and the ability to calibrate the signals produced becomes crucial as deployment times increase. Similarly the volume of reagent use and its chemical stability under oceanic conditions also become very important for devices that are free floating. Devices on moorings deployed in coastal regions with high levels of synoptic variability and strong spatial gradients in water column and sediment properties require high frequency or continuous sampling to resolve processes. Similar types of moorings deployed in remote or hostile marine environments may not require such high frequency sampling but need to be calibrated in situ and maintenance free for periods of a year or more Currently many properties of interest to oceanographers are determined on samples returned to shore-based laboratories. This can be either because of lack of methodology compatible with use at sea or because shipboard space is limited. In many cases because of low analyte concentrations these properties require large volumes of water the shipping of which is both expensive and can present severe logistical problems.

Thus, there are many needs in oceanography that can benefit from the latest developments in analytical chemistry they can be summarised as desires for:

Low power consumption Increased speed of determinations Low detection limits High precision Low maintenance Insensitivity to typical shipboard vibrations and accelerations The ability to be calibrated in situ High specificity for the target analyte

2. Current state of the art Currently oceanographers use a wide range of techniques to gather data at a variety of temporal and spatial scales. These can be divided broadly into shipboard, shore-based and platform-based methodologies. The shipboard determination of a variety of species is undertaken to provide real time sampling feedback as well as to identify and help rectify any sampling problems, particularly for contamination prone elements. Shore-based methodology is applied to analytes for which there is either no methodology compatible with shipboard use, or for which there is no pressing need to make near to real time measurements in the limited space available on research vessels. Currently there are only a few methodologies, mainly for macronutrient species discussed later, available to determine parameters of interest to oceanographers that can meet the power, weight and reliability needed for use on autonomous platforms. It is expected that building on current experience, development of such methodologies will be a high priority for oceanographers in the future. 2.1 Oceanographic sampling Current oceanographic sampling covers a wide range of spatial and temporal scales from single sampling packages containing up to 36 separate samplers deployed from surface ships to high frequency automated sampling by autonomous or remotely operated vehicles. For elements that are found in trace quantities in the ocean but are ubiquitous in commonly used materials, avoiding contamination at the sampling acquisition stage is an extreme driver of the sampling process. For these elements this usually means using specialised sampling equipment (e.g. Teflon-coated sampling bottles attached to plastic-coated metal frames, and polymer based cables for vertical sampling) and careful control during the subsampling processes (e.g. the construction of spaces with class 100 filtered air) to avoid the introduction of contaminants from the relatively contaminated shipboard surroundings. For materials with fewer contamination issues the construction of the sampling equipment is less critical but care has to be taken to avoid introduction of materials into samples that can alias later determinations. Surface seawater samples can be collected either using the ship's continuous pumping system or for

contamination-prone materials, via a towed torpedo-shaped “fish”, deployed typically at a distance of ~5 m from the ship while it is underway, and connected to a deck mounted all-Teflon® diaphragm pump by Teflon®-PVA tubing. In both approaches, sample degassing and filtration can be incorporated in-line and the filtered sample pumped directly to the flow analysis system and/or collected for off-line analysis. The sampling rate from these devices can range from continuous to discrete depending on the property gradients that are being assessed. For autonomous vehicles and fixed moorings, sample intake has to be carefully designed to be "upstream" to avoid contamination from the body of the sampling platform. 2.2 Sub-sampling After the sampling process has been optimised maintaining the integrity of the sample from the point of collection to the point of analysis is critical and provides severe challenges in terms of materials that samples can be allowed to contact, temperature changes etc. Additionally for reactive materials with short lifetimes, sub-sampling time-scales can be critical, and may be eventually addressed more easily using in situ methodology. A major aspect of sub-sampling is whether samples are filtered or not. Most samples are filtered before determinations through 0.45 um or 0.2 um filters. The materials that these filters are constructed from and their pre-cleaning protocols can be very important for both contamination prone work as well as the less contamination prone materials since materials used in the manufacturing process, such as surfactants can have deleterious effects on the chemical methodology used in subsequent determinations. There is a developing interest in characterising the colloidal fraction of a variety of species in the ocean and this has led to the development of a variety of approaches to isolating this fraction, including cross-flow filtration as well as direct pressure filtration using extremely small pore sized filters. It is likely that this interest will continue and extend beyond the current range of analytes. The need to incorporate some kind of filtration process prior to determination into autonomous sampling systems is perceived as a significant problem that will need to be solved. The pretreatment of samples in general, and filtration can be considered part of this, is an evolving area of oceanographic research. The filtration issue is also relevant to the biological accessibility of the fraction being determined, since the availability of the species to particular organisms has important consequences for the success of biological processes in the ocean, a good example of course being the case of Fe. However, at this stage there is not much information available about exactly which of the chemical and physical species of this element are available to organisms and filtration has been adopted more to prevent the particulate phase from being transformed during sample pre-treatment and storage processes. This is particularly important when samples are acidified for long-term storage or as a necessary part of the analytical methodology. Acidification in the presence of

particles will lead to their partial dissolution thus aliasing the determination. However acidification of previously filtered samples will also affect the speciation of the dissolved materials. Thus development of in situ methodologies that do not require sample pre-treatment may provide important insights into the reactivity of crucial micronutrients in the oceans in their natural state leading to a greater understanding of the chemical controls on biological processes. 2.3 Shipboard Analysis Shipboard determination of a variety of species is undertaken to provide real time sampling feedback as well as to identify and help rectify any sampling problems, particularly for contamination prone elements. Flow-based systems using wet chemistry in small diameter tubes (typically 0.5-0.8mm) have proved very popular as they can be fast, have high precision and use only small quantities of reagents. The reproducibility of the timing between reagent mixing and detection does not require complete reaction and they can be easily combined with in line filtration and pre-concentration processes. Additionally, they can be used to detect transient species such as those produced by chemiluminescence and can be automated and connected to continuous underway sampling systems. They also are fairly compact and are insensitive to problems arising from the vertical accelerations experienced on ships. Their major disadvantages are that they tend to be single element specific, and the power and maintenance (associated with replacing peristaltic pump tubing etc.) makes them unlikely candidates for use with autonomous vehicles. The use of wet chemicals also poses issues of chemical stability and also requires large volumes of reagents for long-term deployment. Gas chromatography has also been used extensively at sea largely for determining anthropogenic gas tracers in sea water (chlorofluorocarbons, SF6, etc). The ability to separate gases from the seawater matrix by purging and trapping and the high sensitivity of ECD-GC when coupled with column separation has made this a multi analyte technique for these parameters. However, the drawback of gas chromatography can be obtaining or shipping high purity compressed gases and delivering instrumentation containing radioactive materials to remote locations. 2.4 Shorebased determinations Shorebased determinations are undertaken for the majority of parameters currently determined in oceanography. In some cases this is because adequate shipboard methodology is not available or because there is no pressing need to obtain real time data on space limited ships, or that the determination process is too laborious or slow (e.g. counting decay products) to match typical research cruise logistics. On the positive side, shore-based methodologies usually have higher precisions than can be obtained at sea and also can be conducted in environmental conditions that are much easier to keep clean. It is also much easier to provide for large amounts of gas usage ashore, and to use instruments that are not sufficiently

robust to cope with the vibrations on research vessels and significant accelerations (up to 0.3 G) experienced in some oceanic regions. A variety of techniques, both single as well as multi analyte are used ashore. Various types of mass spectrometry are employed such as Inductively coupled plasma-mass spectrometry (ICP-MS) which can provide data for multiple analytes or isotope ratio instrumentation that permits the very high precisions and is often combined with isotope dilution. The main limitation of shore based determination is the need to ship large amounts of water back from sea, and the problems of storage of these samples and the potential changes in the form of the analyte between sampling and determination times. 2.5 Platform based determinations Currently most parameters that can be determined on autonomous platforms are determined using reagentless techniques such as conduction, spectroscopic approaches, such as for NO3 or light based systems such as fluorometric techniques. The difficulty of developing low power, low maintenance wet chemical methods has limited their application on these platforms. Recent successes in the development of micro-fluidics (lab on chip) for determination of nutrient species shows that wet chemical techniques have the potential to be utilised on such platforms and that this approach may be extended to other analytes that are currently determined using wet chemical methods. 2.6 Standardisation and calibration of instrumental signals

Assuring high quality data is essential to oceanographic studies. Global biogeochemical cycles occur on spatial and temporal scales that require the coordination of multiple investigators from different groups using different methods participating in different research expeditions. Therefore, data quality must be validated at multiple levels of analyses, from a single analyst’s figures of merit to the integration of intermediate data products. This addresses in situ sensors as well as on-line or off-line instruments that are used during a cruise/deployment.

Ultimately, the goal is to reduce the necessity of skilled personnel during

expeditions without compromising data quality and the traceability of the results. This becomes even more important as sensor networks/observatories such as the Coastal Observing System for Northern and Arctic Seas (COSYNA) network become more important and the role of inaccessible remote sensors and analyzers deployed on automated platforms (e.g. FerryBox systems) increases.

Analyses at sea are subject to additional challenges unique to the

environment, which include inclement weather, excessive and irregular vibrations by the ship itself, lack of clean electrical power, spilling or sloshing of reagents, sudden or slow changes in sensitivity throughout a long analytical run (to keep pace

with sample collection), or a general inability to tightly control analytical conditions such as temperature and humidity. While shipboard analyses require the same types of QA/QC checks as land-based measurements, they are usually conducted more frequently when at sea.

To reduce the amount of time highly trained personnel dedicate to

supervising automated systems, methods need to be devised to ensure data quality in an automated and reliable manner. To this end, standards should be determined through automated systems, for example, by extending the flow system of microfluidic systems and using the versatility of Sequential Injection Analysis (SIA) systems to regularly generate standards (from more stable higher concentration standards) and automatically generate and determine spiked samples.

Currently, several methods are employed to ensure that data sets among

different lab groups are validated, which include calibration against an external reference material or intercalibration among other groups making similar analyses. Certified reference materials are available for most physical parameters (e.g., salinity), micronutrients (e.g., nitrate), and trace elements (e.g., dissolved and particulate Fe). In many cases, however, these reference materials are unsuitable proxies for genuine marine samples, due to unnatural analyte concentrations, dissimilar matrices, or disparate sample sizes (to ensure homogeneity). Therefore, many laboratories also intercalibrate using archived or recently collected samples distributed to and analyzed among several labs. While the concentrations are not certified, the intercalibration samples allow laboratories to validate against genuine samples, where concentrations, matrices, and sample sizes are most like those encountered in the environment.

However, analyses of short-lived analytes such as Fe(II) and some radioisotopes (e.g., thorium or protactinium) must be analyzed or processed at sea, and are simply impossible to validate using certified reference materials or redistribution of archived samples. In these cases, multiple laboratories have participated together in intercalibration voyages where large sample volumes can be collected and immediately distributed and analyzed at sea. These intercalibration exercises are inherently infrequent, as limited berthing on research voyages precludes multiple investigators of the same analyte from participating on the same cruise. Therefore, crossover stations have been established across the world, where participants on different voyages sample the same water at the same place. While some natural variability in concentrations is expected, the general distribution of the analyte throughout the water column remains relatively unchanged. Details on recent intercalibration efforts are in Appendix II 2.7 In situ sensors that might operate at the global scale Chemical and biological sensor technologies have advanced rapidly in the past five years. Sensors that require low power and operate for multiple years are now available for oxygen (Kortzinger et al., 2005; Tengberg et al., 2006), nitrate

(Johnson et al., 2002; 2013), and pH (Martz et al.,2009; Johnson et al., unpublished). A variety of bio-optical properties (chlorophyll fluorescence, light scattering by particles, downwelling irradiance at various wavelengths), which that serve as proxies for important components of the carbon cycle (e.g. particulate organic carbon; Bishop, 2009; Boss et al., 2008; Xing et al., 2012), can also be sensed routinely in situ. These sensors have all been deployed successfully for long periods, in some cases more than three years, on platforms such as profiling floats or gliders. Technologies for pCO2 (Fiedler et al., 2013) and particulate inorganic carbon (Guay and Bishop 2002) are maturing rapidly, as well, and have also begun deployments on autonomous platforms. These sensors could serve as the enabling technology for a global biogeochemical observing system that might operate on a scale comparable to the current Argo array (Roemmich et al., 2004). 2.8 In situ Lab on chip and reagent based sensors The minituarisation of existing reagent based chemistry to Lab on chip sizes holds out great promise for the oceanographic community. Since much of the historic work in oceanography was undertaken with such wet chemistry methodology there is a large extant knowledge base for a variety of analytes such as NH4

+, N2O, NO2-, NO3

-, PO4

3-, SiO4

4-, Fe, Mn, pH, Alkalinity etc. Despite the small volumes used by these devices they

are achieving high sensitvity (e.g. NERC and Southampton have achieved LOD <25 nM NO3

- in a lab on chip device (Beaton et al., 2012) and < 0.8 nM PO43- using liquid core

waveguide (Patey et al., 2008), compared with ~400 nM for spectroscopy (Sakamoto et al., 2009). The disadvantages of current state of the art reagent based systems are low measurement frequencies (2-10 samples and hour (Beaton et al., 2012; Moscetta et al., 2009) whereas spectroscopic methods can achieve ~1 Hz, enabling eddy correlation flux determinations, Johnson et al., 2011). The current commercially available in situ reagent systems tend to be large, fragile and need expert users (particularly to make up standards and reagents), have high power and resource (reagent) consumption, and high production (and ownership) costs. As is shown in Table 1, not all reagent-based systems (e.g. Sami-pH/CO2, Systea, Subchem, Wetlabs Cycle-P, CHEMINI) suffer from all these drawbacks. State of the art in situ devices have been developed in various research groups across the world. These all suffer from similar issues and typically optimize performance over robustness and manufacturability and longevity. Systems using liquid core waveguides (LCW) offer the best performance. Here, the sample (water) forms the core of a waveguide formed in a low refractive index tube (typically Teflon AF). Published data shows a LOD for 1 nM nitrite (Adornato et al., 2005) but owing to the use of segmented flow to prevent sample dispersion, the system can only operate to 100 m depth (gas bubbles can’t be used at greater depths). State of the art multi-parametric ship-mounted carbon(ate) sensors using LCW achieve superior performance than required (Wang, Z.A., et al., 2008), but are large, complex and to date only pH measurement has been implemented in situ (Liu, X., et al., 2006). LCW systems are difficult to make

robust and integrated, not least because of problems of flushing and cleaning these long cells, and difficulties interfacing the cells to integrated optical and fluidic systems. This has prevented multifunctional integration and scale up / widespread deployment, despite significant investment in research and development. Trace metal systems have used luminescence sensing to achieve LOD <0.3nM (Okamura et al., 2001).

A

B

Figure 1 microfabricated LOC analytical system A: LOC element for Nitrate and Nitrite (7 nM precision) showing tinted plastic and integrated fluidics and optics; B integrated LOC system with off chip pumps and valves.

Microfluidic and microfabrication technologies used in “Lab on chip” (LOC) devices promise novel solutions to these problems. A handful of laboratories have developed in situ LOC reagent based systems for environmental applications (Beaton et al., 2011, 2012; Fukuba et al. 2011; McGraw et al., 2007; Takagi et al., 2004; Greenway et al., 1999; Floquet et al., 2011; Ogilvie et al., 2011; Sieben et al., 2010; Reroille et al., 2012; Provin et al., 2013). These have demonstrated systems for nutrients, trace metals, and carbonate parameters. These systems dramatically reduce the size and complexity of reagent based systems by integrating all fluidic interconnections and optics (LED based) into a single “chip” based on an optofluidic manifold. The technique potentially brings radical cost reduction and improved sensitivity. A promising approach is to run all systems at ambient ocean pressures (typically up to 60 MPa - 6000 m equivalent) including all electronics, optical, and mechatronic systems. This has a dramatic effect on potential manufacturing costs as expensive high-pressure cases and connectors are no longer required. To achieve high performance (e.g. LOD 25 nM nitrate, Beaton et al., 2012) novel optical approaches have been used. Stray light often limits the performance of absorption cells, but this has been resolved using optically absorbing polymers in a solvent polished polymer monolith (Floquet et al., 2007; Ogilvie et al., 2010). Table 1. Comparison of requirements vs. production scale state of the art biogeochemical sensors. NB to operate on an Argo float or glider a sensor package should have the following spec < 7 L, neutrally buoyant ±50 g (in total, for all sensors used on each float), and low buoyancy change (<20 g), bulk modulus and thermal expansion matched to float an invariant, < 50 J/sample, 2500 m depth rated, >6000 measurements for each analyte

Analyte Required performance:

State of the Art principle limitations in bold critical limitations also underlined

Carbonate system: pH, CO2, DIC, Alkalinity

2 parameters at precision ±0.001 pH, TA/DIC ± 0.1 %, pCO2 ±1 µatm .

Sami-pH: <±0.001 pH, 72J/sample, 4300 samples, 7.6 kg, ~10 L, 600 m (Degrandpre et al., 1995; Spaulding et al., 2011) Sami-CO2: as pH but <±1 µatm, 9000 samples (Degrandpre et al., 1995) Satlantic SeaFET: <±0.001 pH. Drift .005 pH/month, 131mJ/sample, 4.4 L, 70 m (Martz et al., 2010) Contros CO2: <±1 µatm, ~200J/sample, 4.7 kg 2.4 L, 6000 m 1

Nutrients: NH4+, N2O, NO2-, NO3-, PO43-, SiO44-

LOD: <1nM surface open ocean, <100nM coastal ocean and deep sea

SUNA: NO3- only, LOD 400nM, 7J/sample, 1.5 L, 2000 m (Sakamoto et al., 2009; Johnson et al., 2002) Systea Wiz/DPA/NPA: not SiO44-, LOD 100 nM, 10 nM nitrite >108kJ/sample, Wiz 10 L 10 m reagent cassette, NPA 20 L 100 m, DPA 40 L 4500 m (Moscetta et al., 2009) Subchem Fin: LOD 10-50 nM, 3J/sample (3W, more in warm up), ~3 kg, 2.7 L, 600 m Wetlabs Cycle-P: PO43- only, LOD 75 nM, 14 L, 2250 J/sample, 6000 m, reagent cassette2 CHEMINI: LOD >100nM, 9.8 L, 12.6kg, 864 J/sample (Vuillemin et al., 2009)

Micro-nutrients / trace metals (Fe, Mn)

LOD: <400pM surface ocean, <5nM coastal and deep sea

Systea Wiz/DPA/NPA: as above Subchem Fin: as above CHEMINI: as above plus LOD 300nM

Addressing limitations To achieve the LOD (<1 nM) required for open ocean studies, further optimization is required. For example the absorption cell length could be increased (LOD is inversely proportional to cell length for absorption based detection), however this would lead to increase fluidic/reagent/flushing volume and reduce temporal resolution. Alternatively preconcentration (see section 4.1.1) or fluorescence (Bey et al., 2011), or luminescence (Okamura et al., 2001) could be applied. Cavity Ringdown Spectroscopy (CRDS) could also be used. The method is based on placing two mirrors either end of an absorbing sample to achieve multiple passes through the optical cell. This increases the effective path-length, and hence sensitivity, by several orders of magnitude, without increasing the probed volume (Rushworth et al., 2012; Neil et al., 2011). CRDS has recently been demonstrated to enable nanomolar detection limits of nitrite and iron (II) in

1 http://www.contros.eu/products-hydroC-CO2.html 2 www.wetlabs.com/cycle-po4

a bench-top system using optical flow cells with absorption path lengths from 0.1 to 2 mm, probing 20 – 400 nL volumes (Rushworth et al., 2013). With 99.8% reflectivity mirrors, over one thousand passes of light are obtained through the sample, yielding a total absorption pathlength of 1 m from 1 mm cell.

To address cost and complexity of reagent based systems it may be possible to develop in situ micro pumps and valves for lab on chip platforms. This could take advantage of fluoroelastomer membrane based pump and valves (Ogilvie et al., 2011a, 2011b). However this requires development of low power actuators able to operate in in situ conditions – and these currently do not exist. To address required user skill, and also reagent / standard lifetime a promising approach is to use cassette / cartridge based reagent / standard packs. This is implemented by Wetlabs in the cycle P and NH4 systems and in surface systems (see figure 2).

Figure 2 Proprietary reagent cartridge solutions: by TELLABS Aquamonitrix platform (A-C) with cartridges shown in lower part of A and B: D) Wetlabs Cycle-P with reagent and standard cartridges shown in red, yellow and blue (disconnected from sensor to show connector detail).

Within the chemical oceanography community there is concern that particulates and biofouling will limit long-term deployment of in situ fluidic and microfluidic platforms by blocking channels. The data to support this concern is currently limited. However, with simple filtration, and modest antifouling (materials selection, copper) channels have not been blocked in deployments even in fouling prone surface deployments where there is a high particulate load (Beaton et al., 2011, 2012). However, this issue requires further assessment and development. 3. Areas of focus in oceanography Many of the current areas of focus in oceanography are related to the effects of human activities on global climate and the role that the ocean plays in moderating and reacting to these influences. The challenge of understanding the ocean’s role in the global carbon cycle and its response to a changing environment requires an expanded scale of observation in both space and time. Questions regarding the

(D

magnitude of the uptake of anthropogenic carbon dioxide and severity of the resulting ocean acidification (Sabine et al., 2004); ventilation of the thermocline in mode-water-formation areas and associated formation of preformed nutrients (e.g. Sarmiento et al., 2004); rate and spatial distribution of ocean deoxygenation (e.g. Keeling et al., 2009); transport of nutrients (including micronutrient metals) to the euphotic zone in nutrient starved stratified ocean regions (e.g. Jenkins and Doney, 2003) and mechanisms controlling the ocean’s biological carbon pump (e.g. Ducklow et al., 2001) all require measurements on spatial and temporal scales that are rarely achieved using traditional ocean sampling methods. However, in addition to these focused programs, our relative ignorance about the mechanistic operation of the ocean has spawned several large scale oceanic survey programs that aim to answer fundamental scientific questions about the physical (WOCE/CLIVAR), biological (JGOFS) and chemical (GEOTRACES) operation of the ocean. The results of these programs will inevitably lead to new research initiatives, the success of which will be limited by our ability to map the chemical distributions in the ocean at a sufficient resolution. 4. Capabilities of present and emerging analytical chemistry technology This section contains the results of the working group deliberations (see Appendix II for listing and participants). These have been condensed for the sake of brevity, the originals are at: (http://www.soest.hawaii.edu/oceanography/faculty/chrism/COCA/Home.html) 4.1. Sample processing

4.1.1. Pre treatment, pre concentration, and hyphenation Since the development of novel analytical oceanographic methodology will

need to be carefully matched to existing pre-treatment schemes, working groups considered the various aspects of sample pretreatment currently undertaken in oceanography and how that would impact potential new methodological approaches.

Pre-treatment of seawater samples is common to most oceanographic

determinations. There are a variety of reasons for this ranging from addition of toxins to prevent biological growth, separation of dissolved and particulate fractions through filtration, preservation of samples by acid addition for later shore-based determination, and digestion techniques to release analytes from complexed dissolved or particulate forms to make them accessible to analytical methodology. The most common pre-treatment methodology though is that of simultaneous matrix elimination and analyte pre-concentration. Various working groups identified this as one area on which future research and effort should be focused. Key points to be considered are selectivity for the target analyte and compatibility with the prior and subsequent steps of the analytical procedure.

The suitability or necessity of different types of pre-concentration is related

to the type and sensitivity of the final determination technique and thus a variety of different approaches need to be explored. The amount of preconcentration required for sensitivity purposes, and the volume of sample required for the ultimate analytical determination are directly related to each other and inversely related to the ability to remove matrix interferences. The volume of sample required for pre-concentration will also affect the rate at which samples can be processed. For example, large-scale pre-concentrations using solid phase or liquid-liquid extractions require lengthy processing steps that might be difficult to automate and to interface with novel micro-fluidic methodology.

There were several suggestions for new approaches to sample pre-

concentration. The design of novel ligands inspired by research in biological systems that can combine high selectivity with high enrichment factors, and their immobilisation with new support materials is a promising area for research. Another suggestion was the use of complexing agents in combination with magnetic beads as a pre-concentration mechanism for large volume radionuclide determinations. Pre-treatment of samples prior to analyte determination, such as acidification, filtration etc. also presents the issue of ensuring the uniformity of results, and comparability with existing data. Some pre-treatment systems such as the liberation of elements from ligand complexes have slow kinetics, further constraining the approaches that can be successfully linked to automated methodologies. Additionally, since developing multi-element methodologies is clearly of interest, future research should concentrate on pre-concentration and treatment methods that are applicable to multiple analytes. An alternative approach to pre-concentration that is not necessarily linked directly to automated analyte determination is the development of passive sampling techniques. Passive sampling and enrichment of analytes such as metals has great potential as it is simple, economic and can be performed in-situ such as on moorings, autonomous vehicles etc. It also has the added advantage of matrix separation. However, understanding and defining the sampling time window and calibrating such devices will require significant research. It was concluded that research on the development of passive sampling methods, where the analyte enrichment factor is in equilibrium with the environmental concentration could be play an important role in developing new oceanographic methodology. It was also recommended that hyphenation of different analytical techniques might provide useful approaches to the problem of low concentrations and complex matrices in oceanography. As an example, transition metal preconcentration on Sequential Injection Analysis or related platforms for matrix removal could be

connected to liquid chromatography for analyte separation and then coupled to highly sensitive detection techniques such as potentiometry or chemiluminescence for detection. Such a system might provide the basis for ship-based, sensitive, and reliable multielement analysis. What follows are descriptions of current analytical methodology that might be applied to oceanography and the limitations inherent in these methods and potential avenues for future research.

4.1.2. New trends in matrix removal 4.1.2.1. The potential of polymer inclusion membranes in passive sampling and

analyte preconcentration in oceanographic monitoring Most traditional aquatic monitoring programs rely on ‘grab sampling’, which is often referred to as ‘spot sampling’ or ‘bottle sampling’. Grab sampling involves collection of a water sample at a particular spot at one time. As such, a grab sample reflects the water composition only at the point and time that the sample was collected. This information can be misleading where the levels of the compounds of interest fluctuate. To overcome this problem continuous or frequent grab sampling will be required. Such monitoring programs are often time consuming, expensive and of limited success. This situation has created the need for monitoring approaches that can provide more representative measurements of water quality. One such approach is based on a technique known as ‘passive sampling’. Passive samplers can be deployed for extended periods of time (from days to weeks or even months) at multiple locations within the aquatic system of interest and yield time-weighted average concentrations of the chemical species of interest. This approach dramatically increases the likelihood of rapid and accurate identification of intermittent sources or sinks of the chemical species of interest. In addition, passive samplers are far less expensive than active samplers since they do not incorporate moving parts and do not require a power source for conducting the sampling process. They also allow preconcentration of the chemical species of interest which simplifies their analytical determination. Most passive samplers are not only inexpensive but also very small and mechanically strong and are suitable for deployment in almost any environmental condition.

In most cases the sampling process is based on diffusion across a hydrophilic or hydrophobic barrier, which is usually a porous membrane, into a receiver phase. Passive sampling is a relatively new monitoring technique which has been applied predominantly to fresh water systems. There are only a limited number of applications to marine systems and most of these applications are in coastal waters. The main types of passive samplers that have been used for monitoring of chemical species in seawater so far are: 1) Polar Organic Chemical Integrative Samplers (POCISs)

A typical POCIS consists of a solid sorbent enclosed between 2 microporous hydrophilic membranes (e.g. polyethersulfone). Water-soluble chemical species can diffuse through the membranes to the sorbent where they are trapped while larger particles cannot pass through the small membrane pores. After sampling, the target chemical species accumulated into the sorbent are extracted into a suitable organic solvent and the extract is often analyzed by an appropriate chromatographic technique. POCISs have been used for monitoring of organic species such as pharmaceuticals, alkylphenols, pesticides and PAHs (Harman et al., 2011). 2) Chemcatcher

A typical Chemcatcher consists of a watertight polytetrafluoroethylene (PTFE) or polypropylene cylindrical container where a 47 mm 3M EmporeTM adsorbent polymeric disk is located which can be covered by a thin diffusion limiting microporous membrane. After retrieval from the environment the disks are processed as the sorbents of POCISs. Chemcatcher samplers have been used for monitoring of pollutants such as Hg (Aguilar-Martinez et al., 2011), organotin (Aguilar-Martinez et al., 2011) and pesticides (El-Shenawy et al., 2010). 3) Diffusion Gradient in Thin-film (DGT) samplers.

A typical DGT sampler consists of a hydrogel layer incorporating a compound that strongly binds the analyte. The binding layer is separated from the aquatic environment by a diffusive layer of hydrogel (e.g. hydrated acrylamide diffusion gel) and a filter membrane. DGT samplers have been used for the determination of Al(III) (Panther et al., 2012)and phosphate (Panther et al., 2010). 4) Membrane strips These samplers employ different polymeric materials suitable for the adsorption of various organic species such as pesticides (St George et al., 2011), PCBs (St George et al., 2011, Cornelissen et al, 2008) and persistent organic pollutants (Fernandez et al., 2012). 5) Semi-Permeable Membrane Devices (SPMDs).

These samplers employ a passive dialysis process where the analyte diffuses across a semi-permeable porous or non-porous membrane into a receiver organic or aqueous solution. An SPMD with a ferrihydrite layer separated from the marine environment by a hydrophilic porous membrane has been used for phosphate monitoring (O'Brien et al., 2011).

POCIS, membrane strips, Chemcatcher and DGT samplers operate on similar principles (i.e. use of a solid sorbent material as a receiver phase) and a series of pretreatment steps (e.g. extraction, desorption) are required prior to the analytical measurement of the preconcentrated analyte. Some of these steps involve the use of large volumes of organic solvents, which is counter to the current trend towards environmentally friendly technologies. Unlike these samplers SPMDs may incorporate a receiver solution rather than a solid receiver phase which simplifies the determination of the accumulated pollutants. However, both passive dialysis

across a porous membrane or diffusion across a neutral non-porous membrane offers limited selectivity, which is determined by the membrane pore size or the membrane/solution distribution ratio of the analyte. In addition, passive dialysis across a porous membrane has virtually no preconcentration capabilities, which is often crucial for the detection of chemical species at trace levels. Neutral non-porous membranes such as silicone membranes are not suitable for the transport of charged species. These limitations can be overcome by the use of supported liquid membranes (SLMs). SLMs are microporous hydrophobic membranes impregnated with an organic solution of the extractant (membrane liquid phase), which is retained in the membrane pores by capillary forces. However, SLMs have limited lifetime due to the leaching of the membrane liquid phase into the aquatic environment and the receiver phase (Nghiem et al., 2006).

Polymer inclusion membranes (PIMs) are a relatively new type of self-

supporting liquid membranes. They have shown considerable promise for the selective separation of both metallic and non-metallic chemical species (Nghiem et al., 2006, Almeida et al., 2012). They are homogenous, optically transparent and flexible materials, incorporating a base polymer, such as polyvinyl chloride (PVC) or cellulose triacetate (CTA), and a suitable extractant (e.g. Aliquat 336, di(2-ethylhexyl) phosphoric acid (D2EHPA), Cyanex 272). In some cases a plasticizer/modifier can also be added to improve the homogeneity and/or the extraction and transport properties of the membrane. PIMs offer an attractive alternative to conventional solvent extraction by drastically reducing or completely eliminating the amount of solvents required. Similarly to SLMs these membranes also allow the simultaneous performance of the extraction and back-extraction processes. The extractant, often referred to as carrier, transports the chemical species of interest across the membrane between the source and receiver solutions after forming a complex or an ion-pair at the source solution/membrane interface which is dissociated at the receiver solution/membrane interface thus releasing the chemical species into the receiver phase. This facilitated transport allows mass transfer against the concentration gradient without the application of an external force (e.g. electric field).

These features of PIMs are particularly useful in the analysis of compounds at trace levels when preconcentration of the analyte is required prior to its analytical measurement. By varying the membrane composition in addition to the composition of the receiver solution it is possible to control the rate of membrane mass transfer of the target chemical species. This allows the selection of a transport rate, which is appropriate for the duration of the sampling period and the expected concentration of the target chemical species in the aquatic system. In this way, saturation of the receiver solution with the target chemical species can be avoided.

4.1.2.2. New ligands and new support materials There is a trend to look for new ligands (and support materials) with suitable stability constants for the target analyte to be incorporated in membranes and other support materials. This way, sampler units incorporating these chelating agents can be used to both collect and enrich the analyte at the same time. Additionally these

ligands can be used to achieve speciation, if they target a specific analyte form. Considering that some ligands can present chromogenic or fluorogenic properties, they can also be possibly used to provide in-situ detection. 4.1.3. Separation Several new technologies, not presently used in oceanography are of potential interest for further development for sample handling (preconcentration), separation and measurement. Others, such as sequential injection analysis are platforms that have seen some use but probably can have a broader use. There were also novel ideas discussed around measurement techniques for specific measurement problems. Separations, beyond the steps already used during preconcentration/matrix isolation are not currently used much in on-board measurements. However laboratory measurements do routinely use chromatographic separations with various detection methods for measuring organics in ocean water as well as dissolved gases, e.g., CFCs. Advances in miniature portable gas chromatography and capillary liquid chromatography have made such techniques attractive for shipboard measurements. Capillary monolithic columns are available that can perform extremely fast analysis at high speeds. Separation of a major suite of UV absorbing ions in sub-minute time scales have been shown to be feasible with silica monoliths dynamically or statically coated with cationic surfactants. HILIC (hydrophilic interaction chromatography) stationary phases that would allow ready separation of extremely polar substances like urea from other organics or the salt matrix are now available. Open tubular ion chromatography although not commercially available, has been shown to be a robust, high-speed separation technique capable of separating ions at a very low pressure while still generating a large number of plates. Electrophoresis is one of the major modes of separation on a microfluidic chip. The potential of electrophoretic analysis in oceanography may be limited, however, as samples of high ionic strength cannot be electrostacked for preconcentration. It may however be possible to preconcentrate analytes by isotachophoresis before electrophoretic separations. 4.2 Reagent-less methodology One limiting factor in long-term and in-situ deployment of chemical methods for oceanographic applications is reagent stability. Methodology in which the reagents are created in situ can avoid these problems. Several novel ideas for developing reagentless chemistry methods were suggested. These were inspired by the electrochemical work from Laboratoire d’Etudes en Géophysique et Océanographie Spatiales (LEGOS) on the reagentless determination of phosphate and silicate via molybdenum blue chemistry that has already been developed and was presented in a poster.

The potential to extend this type of methodology to phosphate was advanced where the measurement could be made using a flow-through cavity where phosphate is captured on an iron electrode the exposed surface of which is oxidized to form iron oxyhydroxide that has a very high affinity for phosphate. This electrode would then be held at a negative potential to release the phosphate while simultaneously molybdate is released by anodic dissolution of a solid molybdenum electrode. The molybdophosphate thus formed would be reduced at a gold electrode to make molybdenum blue then measured by direct optical absorbance across the cavity or by using a bifurcated fiber and using the gold surface as a reflector (an excellent reflector in the far red). A second reagentless measurement concept advanced involved the measurement of ammonia that uses as a stepping stone the principle of forming NH3 by alkalinization of the sample, diffusing the NH3 across a membrane into a receptor containing a small concentration of an acid; the conductivity decrease is taken as due to ammonia. In this concept seawater flows through a chamber divided by an ion exchange membrane. The cathode is placed close to a gas permeable membrane, on the other side of which, pure water, prepared by electrolytic deionization of seawater, flows. The conductivity of this water is measured with or without the introduction of a small amount of HCl that is electrolytically generated from seawater, by migrating chloride into the measurement chamber through an anion exchange membrane. A third measurement concept relates to determination of urea. Urea is a very weak base, protonated urea has a pKa of 0.1. Urea will go through a mixed bed ion exchanger without being removed (this deionization can also likely be electrolytically accomplished using membranes – a configuration permitting continuous use). Acid can then be added downstream before preconcentrating the urea on a cation exchanger. When the acid is replaced with water, the urea will no longer be retained. The liberated urea can be photo/thermally decomposed to make NH3 and CO2 that can be detected by a variety of means. As described above electrochemical techniques can be used to produce reagents to adjust sample pH through in situ generation/consumption of protons using ion exchange membranes. Electrochemical approaches can also be used to generate active reagents in situ from more stable precursors such as sulfite release from hydroxymethanesulfonate. Electrolysis or electrodialysis can be used to produce chlorine/hypochlorite from abundant NaCl; this could then be used as a periodic prophylactic remedy for biofouling. It was recommended that research to create electrochemically active reagents that can be converted into useful forms required for analytical methodology is needed. Additionally it was suggested that electrochemical approaches could be used to eliminate ionic interferences such as bromide in the optical determination of nitrate.

4.3. Detection 4.3.1. Mass Spectrometry in Oceanography

Currently, the predominant use of mass spectrometry (MS) in the field of oceanography is in shore-based laboratories. Current MS instrumentation is either too resource demanding (e.g., typical commercial instruments) or not sensitive enough (e.g., current miniature platforms) to warrant their use onboard ships, much less in situ. MS in oceanography is predominantly used for elemental analysis, including ultra-trace analysis of metals ranging from iron to aluminum to thorium (although there is a small and emerging interest in determination of organics). While it was mentioned that the ultimate need was an ICP-MS that can fit in a shoebox and operate underwater with no need for gases, such achievements are not likely in the near future. Instead, novel sample collection (addressed in a different section of this report) or modified laboratory analysis schemes might be viable to reduce the current burden of ocean water sample volumes that are commonly returned to laboratories following scientific cruises for elemental analysis. Some alternate technologies to traditional ICP-MS-based analytical workflows that could be used to address either reduction of required resources or the need to reach extremely low levels of sensitivity included solution cathode glow discharge (SCGD), proton burst spectroscopy, or the incorporation of a charge detector on state-of-the-art (not previously reported), circulating Time Of Flight instruments (TOF). Whereas SCGD could provide a less resource intensive alternative (miniaturized and low to no gas consumption) to inductively coupled plasma - atomic emission spectroscopy (ICP-AES), its sensitivity is not sufficient to replace current ICP-MS capabilities. Both proton-burst spectroscopy (a low pressure laser fluorescence approach to measure elements in the midst of supersonic expansion) and charge detection TOF could offer opportunities to amplify the signals for very low abundance analytes, such technologies though are either in their infancy or are still conceptual ideas which would need further evaluation. An inherent problem with MS though is that the transfer efficiency of the ions (from source to detector) rarely exceeds a few percent, and this is an ultimate limitation for the measurement of attomolar concentrations. To make more use of modern and established MS techniques, the use of electrospray ionization or matrix-assisted laser desorption/ionization for organic/inorganic iron speciation might be viable. These soft ionization approaches followed by tandem mass spectrometry could be useful for example in identifying and discriminating between iron-bound forms in the aquatic environment. Additionally, ambient ionization (AI) techniques hold promise for in situ analysis strategies. AI is well known to be able to promote ionization of various analytes in the presence of high background sample matrices. However, most of these techniques do not provide reliable quantitative information or they lack adequate sensitivity to be of real use in an oceanography setting.

While it is likely is that in the future there may be the development of more powerful (but less power-consuming) MS instrumentation in forms that could make them feasible to bring aboard ships, currently, the best areas for improvement in this field appear to be in the traditional shore-based laboratory setting. If more efficient sample preconcentration techniques (which could be used shipboard) could be coupled with more sensitive detection techniques for elemental analytes, then the current burden of the large volumes of sample that need to be collected for these types of analyses could be reduced significantly. Finally, the analytical chemistry community recommended that chemical oceanographers look beyond traditional methods of concentration quantification using ICP-MS towards more innovative approaches. One example of this is metal quantification using PCR after the metal is bound to a ligand attached to a known oligonucleotide (modified after Mirkin's work at Northwestern). Another example is metal pre-concentration onto ligand-bound antibodies, followed by analysis of antibody-bound cells using ICP-MS (modified after DVS Science research using rare earth elements bound to antibodies). Although procedural blank and detection limit issues are unexplored in these kinds of techniques, these innovative ideas could encourage chemical oceanographers to look toward emerging quantification fields in the biomedical community for novel analytical techniques.

4.3.2. Optical methods

Optical-based analytical methods offer a wide range of instrumentation for the detection of dissolved gases, isotopes, analytes and organic molecules in seawater. Fluorescence spectroscopy (e.g., excitation emission fluorometry, lifetime sensing measurement, and pulse amplitude modulated) is one of the most resourceful techniques to assess the physiology of phytoplankton, the concentration of elements such as O2 or Zn or to measure the pH of seawater, for instance. This instrumentation also has very promising potential for extreme miniaturization. Although photobleaching can limit the sensor lifetime as well as the range of analytes measurable, other materials besides organic and organometallic dyes may be highly suited for their fluorescent properties (e.g., quantum dots). Liquid core waveguide-based luminescence detectors have demonstrated potential for substantial increases in detection sensitivity, but there also can be large potential drawbacks to this approach. These include high sensitivity to bubble formation and to biofouling that impairs light flow. Unjacketed wave-guides (e.g., water jet flow or porous hydrophobic tubing) might offer solutions to these issues. Finally high end emerging spectroscopic methods (cavity ring down laser and integrated cavity output spectrometry) offer promising novel analytical advances to sensor development for isotopes, dissolved gases, phosphate, silicate, iron, and other analytes.

4.3.2.1 Zero- or low-background methods

Another approach to the problem of attaining low detection limits is to develop methods of analysis that have very low or zero background levels. One example of such methods that are already in use is chemiluminescence. Another that deserves more widespread consideration is fluorimetry, for both atoms and molecules. Such methods have already been shown to be capable of single-molecule or single-atom measurement, and might overcome some preconcentration difficulties currently faced in oceanographic analysis. When ionized, both atoms and molecules can be stored for extended times in electrostatic traps, similar in design to ion traps used in mass spectrometry. Those charged species can then be interrogated by means of their fluorescence. Significantly, each atom or molecule can then be repeatedly excited, increasing the number of fluorescence photons that can be captured from each entity, making the approach much more efficient than mass spectrometry, in which each entity can produce at most only a single detector event. The same general concept can be applied also to uncharged (neutral) atoms or molecules by use of magneto-optic traps. Although these are more complicated than ion traps, such devices expand the range of species that can be measured significantly. 4.3.2.2. Radioluminescent light source Photons can be generated through the interaction of radiodecay particles (beta or alpha particles of gamma rays) with suitable media. Possible vehicles for such photon generation include scintillation, Bremsstrahlung, and Cerenkov radiation. Each incoming particle can, by means of these processes, generate a shower of photons, over time scales that range from nanoseconds to femtoseconds. In addition, the repetition rate of the photon bursts can readily exceed a million per second. The result is a power-free light source that can run unattended for extended periods (years to decades) and which enables in situ absorption, fluorescence, and time-resolved fluorescence measurements to be made. Such combinations seem naturally suited for on-site, in situ, or shipboard analyses. 4.3.3. Electrochemistry Electrochemical analysis (e-chem) has been, and continues to be, an integral detection technology for a variety of chemical analytes and can be configured in different formats to accomplish amperometric, potentiometric and conductometric readout of different targets. In addition, e-chem can be configured as a stand-alone unit for in situ sensing applications and also, as a hybrid technique to be coupled to other analytical processing steps, such as a detector for separations in any format. The limits-of-detection for e-chem are highly variable and dependent on the format of e-chem detection used and scaling issues; smaller electrodes can provide enhanced detection capabilities. Finally, the supporting equipment required for e-

chem can be packaged into small instruments appropriate for measurements in the field, such as shipboard measurements. Several different e-chem detection technologies were discussed, including capacitively coupled contactless conductivity detection (C4D) and contact conductivity detection. In both cases, these detection technologies have been interfaced to various separation techniques with a broad range of analytes that could be transduced. Redox-based detection, such as anodic stripping voltammetry, could provide pre-concentration capabilities, excellent LODs and the ability to analyze multiple analytes simultaneously as long as their half-wave potentials are sufficiently different. Interestingly, complete instruments that carry out ASV can be packaged into a small instrument and were stable enough for shipboard measurements. Another issue is electrode material, especially for ASV; while dropping mercury electrodes probably do not have the robustness for remote measurements, carbon electrodes coated with bismuth have been shown to be viable alternatives. Sonoluminesence (emission produced indirectly from sound energy) and Laser Induced Breakdown Spectroscopy (LIBS) were suggested as relatively unexplored methods for oceanographic trace metals that could be extremely beneficial. Combining electrochemical concentration/stripping techniques with volumetric concentration to further enhance enrichment factors and methods to concentrate difficult metals like iron could be extremely useful. Finally, e-chem can be coupled to various fluidic platforms resulting in autonomous systems that can provide up-front processing of seawater samples followed by analysis and detection. Additionally it was suggested that electrochemical approaches could be used to eliminate ionic interferences such as bromide in the optical determination of nitrate. 4.4. Fluidic systems 4.4.1. Flow analysis Flow injection analysis (FIA) is widely used for the automation of wet chemical techniques in the field of oceanographic chemistry and significant advances have been made in achieving the low detection limits required by oceanography. There are however a few limitations which could be addressed by advances in flow based techniques. Several shortcomings of existing techniques emerged in the course of discussions:

• instrumentation requires the close attention of skilled personnel and can be prone to failure,

• reagent consumption requires the transportation of large volumes of liquids, • many sample pretreatment steps are manual and are dependent on the expertise of

the oceanographer Given the low detection limits required for many of the analyses, reagent blanks can be significant issue. Sequential injection analysis (SIA) with associated specializations such as bead injection analysis (BIA), lab-on-valve (LOV), and Zone Fluidics (ZF) offer paths forward that should be seriously considered by oceanographers. These techniques offer the possibility of addressing some of the limitations mentioned above and also further extending the capabilities of automated wet chemistry. In particular, SIA, LOV and ZF promise significant reduction in reagent use and waste generation. A further benefit is the simplification of required instrumentation, which results in a reduction in complexity and physical size. Both LOV and ZF techniques attempt to incorporate more of the sample handling steps in the flow analysis device. Present unit operations that have been successfully incorporated into these devices include

• solid phase extraction and enrichment • bead injection • uv, thermal, and chemical digestion • solvent extraction • distillation • in-situ reagent generation • sample heating • dilution • matrix modification e.g. pH adjustment • bubble elimination

The desire in oceanography for matrix elimination and pre-concentration of analytes can be tackled in µ-SIA by using beads that are aspirated into the sample flow path and are used as a renewable surface onto which the analytes may be adsorbed. With specialised functional groups the beads can simultaneously concentrate the analyte while flushing away the interfering matrix components. As these beads can be renewed in every cycle, saturation or sample carryover effects are eliminated. In this scenario, the enrichment, matrix removal, derivatizing and detection steps can be carried out in a single valve. Another task presently left to the operator of the instrument that has been successfully deployed to the flow-based analyzer includes automated generation of calibration standards by on-line dilution of a single stock standard. This approach is simple to automate in modern flow-based analyzers and eliminates operator errors in the preparation of standards. Of course it is imperative to verify the concentration of the stock solution by validating the calibration using a check standard or standardized reference material.

In some recent work, advantages have been found in moving certain unit operations close to the sampling point and providing the sample-analyzer interface with some functionality to enrich, dilute, and filter. By carrying out these operations close to the sample some advantages in managing contamination may be realized. It was noted that dialogue between oceanographers and system developers highlighted certain areas where improvements in vulnerability of the connectors and narrow bore tubing could be tackled. Additionally, adding other system diagnostic tools such as calibration tracking, pressure monitoring, and the use of control samples will further enhance the robustness of instrumentation and reduce dependence on an expert user. Limited budgets have often forced oceanographers to build their own systems. With forethought and budgeting during the grant-writing stage, provision can be made to include commercial instrumentation that will hopefully include the latest technology optimized for robustness. Feedback and involvement of oceanographers in defining system specification at an early stage in the instrument development cycle will ensure that developed instrumentation meets the unique needs of this market sector. 4.4.2. Microfluidics (also see section 2.8 lab on chip) Microfluidics is an enabling technology that can take many of the unit operations required for processing complex samples and fully automate the entire processing pipeline. As an example, trace metal analysis requires several processing steps to secure results from the measurement; steps include sampling, matrix removal, pre-enrichment, analysis and detection. In many cases, microfluidics can generate a system that can fully automate these unit operations into an autonomously operating system that does not require operator intervention and also, has the added benefit of reducing the amount of reagents required for the measurement. Several examples of this capability were shown in the meeting, including genetic analysis of samples and optical measurements of trace metals. Various unit operations that can be transitioned to a microfluidic platform include pre-enrichment, removal of matrix interferences, separations, mass spectrometry, electrochemical detection, optical readout modalities and even flame-based detection (fluorescence emission spectroscopy). The challenge with microfluidics, in regards to oceanographic measurements, is the small sample volumes that can be accepted by the platform (on the order of nL to uL) and the large sample volumes typically encountered in oceanographic measurements, for example the trace analysis of heavy metals. However, during presentations at the workshop, technologies were discussed that could sample relatively large input volumes and pre-concentrate targets using uniquely designed support structures that have ligands attached to them that are appropriate for specific analyte targets, such as IDA or EDTA-type derivatives. These devices were found to provide nearly 106-fold enrichment factors

with the specificity determined by the affinity of the ligand for its cognizant target. Other unit operations that were demonstrated as appropriate for transitioning to microfluidics were separation platforms (electrophoresis, chromatography), biochemical reactions, and various detection strategies, such as fluorescence, conductivity and amperometric detection. However, there are others as well, such as mass spectrometry. The challenge with microfluidics is the accessibility of these new systems to the general oceanographic community. There are several issues along these lines:

i. Understanding that scaling factors are integral to the design approach. Here, effects of reducing the analysis platform size must be considered, such as effects of column length on separation efficiency.

ii. Wall effects. Because of the high surface-to-volume ratio associated with any microfluidic platform, the effects of wall chemistry must be considered as to the proper operation of the device. Examples here include non-specific adsorption artifacts and fouling issues. The use of plastics was discussed because these materials have a diverse array of surface properties that can be utilized for specific application areas. Also, the surface properties of these materials can be easily modified using for example, plasmas or UV light. These modifications can provide the ability to covalently attach ligands to their surfaces for enrichment purposes.

iii. Producing devices or systems for testing. This issue was somewhat ameliorated by the potential use of replication-based technologies, such as embossing and injection molding that can produce a large quantity of devices at low cost and with high fidelity.

iv. The time and resources required to generate new, and in some cases paradigm-shifting assay strategies. It was concurred that some development time must be incurred to allow testing and validation of new platforms.

In summary, it was generally agreed that most analytical processing steps that are currently or could be envisioned in the broad area of chemical and even biochemical analysis of the ocean could be transitioned to a microfluidic platform with several advantages that could be realized. These include:

i. Full process automation, reducing or even eliminating the need of an operator to carry out the assay following sample loading.

ii. Reduce reagent requirements. In many cases, reagents could be pre-loaded into the fluidic device that could provide enhanced stability and also, high assay reproducibility.

iii. Reduce processing time and with the ability to run many samples simultaneously, significantly increasing throughput.

iv. Enabling the ability to carry out new processing or analytical methodologies that are currently inaccessible for oceanographers. This will provide the opportunity to significantly increase the available tools for oceanographers to expand the number of analytes in various measurement scenarios with better reproducibility.

v. The level of integration is highly variable and can be expanded to include not only chemical analysis (both organic and inorganic), but biochemical as well, such as for oceanographic genomics.

vi. The support peripherals must be miniaturized as well to realize the delivery of fully operational instruments that can potentially occupy nearly 1/10 the space that current FIA or SIA instruments currently require. The support peripherals include valves, pumps, data processing electronics and detection equipment (optical, electrochemical or others). This is an area of research that really requires much attention.

5. Recommendations

The challenges in chemical oceanography of low detection limits, in a complex matrix with significant contamination issues has led to the following recommendations:

1. Hyphenation of existing techniques holds promise particularly in the case of preconcentration and matrix elimination which appear to be a major problem in many determinations, particularly those at very low concentrations or where interfering materials seriously degrade detection limits. There are several existing methodologies, which have already shown that they can achieve these results or are worthy of future attention from the research community. Fluid or microfluidic approaches using immobilised complexing agents on resins, on columns or on disposable beads could be used in shipboard or laboratory settings. Development of novel complexing agents using recent developments in the biological field can also be the basis for new highly specific pre-concentration and detection systems. Electrochemical methodology can also be used for pre-concentration of many elements and can be hyphenated to a variety of other instrumentation for final analyte determination. Passive sampling with membranes can be used for in situ processes and may play a role in pre-concentration from large volume samples destined for shore-based determinations.

2. For detection techniques the present emphasis on fluorescence and chemiluminescence is promising. The exceptional features of electrochemical methods for speciation, distinguish between free and bound metal ions, are very useful and should be considered and applied. Mass spectrometry is now widely used by oceanographers in laboratory settings with future developments in may be possible to deploy on board ships, among its many new variants that are being developed, solution cathode glow discharge (SCGD) is very promising.

3. Flow based technologies, microfluidics and sequential injection, are well suited to integrate into some of the techniques outlined above in a fully automated fashion. While some air segmented systems are still being use by the oceanographic community they are being replaced by flow injection. Sequential injection which is more robust and uses less reagents than flow systems has been mainly used in the laboratory and on board ships, the advantages of these microfluidic systems makes them potentially suitable for future deployment in autonomous platforms.

4. Microfluidic based chemical sensors (Lab on Chip) are now being successfully deployed for a few parameters, and it is clear that this technology will play an increasing role in determinations as new methodology is developed that is compatible with the format of these devices. Anticipated problems for this kind of platform from bio-fouling and blockages do not appear to have materialised.

5. The current dominant interest in characterising the oceanic carbon cycling is likely to continue driving a demand for research into developing new methodologies that can provide increased data gathering in remote areas and at a reduced cost for the many parameters that are believed to drive the oceanic C cycle.

6. Enabling collaborative research among oceanographers, analytical chemists, and engineers that is necessary to develop the next generation of sensing capacity will require new strategic approaches at the funding agencies that support this work. The workshop participants recognize that there currently is no capacity for initiating new specialized funding programs at for example NSF. However, adopting new strategies among their existing programs could help create new synergies that would facilitate new sensor development research. There are currently three main stumbling blocks. First, there is little community or programmatic structure that bridges between the distinct disciplinary fields of oceanography, analytical chemistry and engineering. For example, it is difficult for oceanographers with concepts for new sensing approaches to find engineering research partners to collaborate with on proposals, and vice versa. Secondly, the review process in programs (e.g., engineering) is heavily biased towards the programmatic discipline rather than obtaining a more expert multidisciplinary assessment of proposal strengths and weaknesses. Readjustment of NSF and other programmatic approaches to deal with these issues could strongly stimulate ocean sensor development without significant increases in the funding base for sensor research.

Acknowledgements

This meeting was supported by funds from the National Science Foundation's Chemical Oceanography program and Chemical Imaging Program through grant OCE 1224874 to Chris Measures and Purnendu Dasgupta. We are particularly indebted to Ed Boyle and Jarda Ruzicka for help in planning the meeting and to Mariko Hatta and Maxime Grand for facilitating logistics during the meeting. This is SOEST contribution XXXXX.

References Adornato, L.R., et al., Continuous in situ determinations of nitrite at nanomolar concentrations. Deep-Sea Research Part I-Oceanographic Research Papers, 2005. 52(3): p. 543-551. Aguilar-Martinez, R., et al., Mercury and organotin compounds monitoring in fresh and marine waters across Europe by Chemcatcher passive sampler. Int. J. Environ. Anal. Chem., 2011. 91 (11): p. 1100-1116. Almeida, M.I.G.S., et al., Recent trends in extraction and transport of metal ions using polymer inclusion membranes (PIMs). J. Membr. Sci., 2012, 415-416: p. 9-23. Beaton, A.D., et al., An automated microfluidic colourimetric sensor applied in situ to determine nitrite concentration. Sensors and Actuators B-Chemical, 2011. 156(2): p. 1009-1014. Beaton, A.D., et al., Lab-on-Chip Measurement of Nitrate and Nitrite for In Situ Analysis of Natural Waters. Environmental Science & Technology, 2012. 46(17): p. 9548-9556. Bey, S.K.A.K., et al., A high-resolution analyser for the measurement of ammonium in oligotrophic seawater. Ocean Dynamics, 2011. 61(10): p. 1555-1565. Bishop, J.K.B. Transmissometer measurement of POC, Deep-Sea Research Part I, 1999,46 353-369 DOI: 10.1016/S0967-0637(98)00069-7 Cornelissen, G., et al., Freely dissolved concentrations and sediment-water activity ratios of PCDD/Fs and PCBs in the open Baltic Sea. Environ. Sci. Technol., 2008, 42: p. 8733-8739. Degrandpre, M.D., et al., IN-SITU MEASUREMENTS OF SEAWATER PCO(2). Limnology and Oceanography, 1995. 40(5): p. 969-975.

El-Shenawy, N.S., et al., Comparing the passive and active sampling devices with biomonitoring of pollutants in Langstone and Portsmouth Harbour, UK. J. Environ. Sci. Technol., 2010, 3 (1): p. 1-17. Fernandez, L.A., et al., Passive sampling to measure baseline dissolved persistent organic pollutant concentrations in the water column of the Palos Verdes Shelf Superfund Site. Environ. Sci. Technol., 2012, 46 (21): p. 11937-11947. Floquet, C.F.A., et al., Nanomolar detection with high sensitivity microfluidic absorption cells manufactured in tinted PMMA for chemical analysis. Talanta, 2011. 84(1): p. 235-239. Fukuba, T., et al., Integrated in situ genetic analyzer for microbiology in extreme environments. Rsc Advances, 2011. 1(8): p. 1567-1573. Goldberg, E.D., (editor), ChemRawn: Modern chemistry and chemical technology applied to the ocean and its resources. Appl. Geochem., 3, 1, 1988. Greenway, G.M., S.J. Haswell, and P.H. Petsul, Characterisation of a micro-total analytical system for the determination of nitrite with spectrophotometric detection. Analytica Chimica Acta, 1999. 387(1): p. 1-10. Guay, C, K.H, J. K.B Bishop. A rapid birefringence method for measuring suspended CaCO3 concentrations in seawater, Deep-Sea Research Part I, 2002, 49,197-210 Harman, C., et al., Field comparison of passive sampling and biological approaches for measuring exposure to PAH and alkylphenols from offshore produced water discharges. Mar. Pollut. Bull., 2011, 63 (5-12): p. 141-148. Johnson, K.S. and L.J. Coletti, In situ ultraviolet spectrophotometry for high resolution and long-term monitoring of nitrate, bromide and bisulfide in the ocean. Deep-Sea Research Part I-Oceanographic Research Papers, 2002. 49(7): p. 1291-1305. Johnson, K.S., et al., Nitrate and oxygen flux across the sediment-water interface observed by eddy correlation measurements on the open continental shelf. Limnology and Oceanography-Methods, 2011. 9: p. 543-553. Liu, X., et al., Spectrophotometric measurements of pH in-situ: Laboratory and field evaluations of instrumental performance. Environmental Science & Technology, 2006. 40(16): p. 5036-5044. Martz, T.R., J.G. Connery, and K.S. Johnson, Testing the Honeywell Durafet (R) for seawater pH applications. Limnology and Oceanography-Methods, 2010. 8: p. 172-184. McGraw, C.M., et al., Autonomous microfluidic system for phosphate detection. Talanta, 2007. 71(3): p. 1180-1185.

Moscetta, P., et al., Instrumentation for continuous monitoring in marine environments. Oceans 2009, 2009: p. 10 pp.-10 pp. Neil, S.R.T., et al., Broadband cavity-enhanced absorption spectroscopy for real time, in situ spectral analysis of microfluidic droplets. Lab on a chip, 2011. 11(23): p. 3953-3955. Nghiem, L.D., et al., Extraction and transport of metal ions and small organic compounds using polymer inclusion membranes (PIMs). J. Membr. Sci., 2006, 281: p. 7-41. NRC. Applications of Analytical Chemistry to Oceanic Carbon Cycle Studies Washington, DC: The National Academies Press, 1993 O'Brien, D.S., et al., Method for the in situ calibration of a passive phosphate sampler in estuarine and marine waters. Environ. Sci. Technol., 2011, 45: p. 2871-2877. Ogilvie, I.R.G., et al., Temporal Optimization of Microfluidic Colorimetric Sensors by Use of Multiplexed Stop-Flow Architecture. Analytical Chemistry, 2011. 83(12): p. 4814-4821. Ogilvie, I.R.G., et al., Reduction of surface roughness for optical quality microfluidic devices in PMMA and COC. Journal of Micromechanics and Microengineering, 2010. 20(6): p. 065016 (8 pp.)-065016 (8 pp.). Ogilvie, I.R.G., et al., Temporal Optimization of Microfluidic Colorimetric Sensors by Use of Multiplexed Stop-Flow Architecture. Analytical Chemistry, 2011. 83(12): p. 4814-4821. Okamura et al., Development of a deep-sea in situ Mn analyzer and its application for hydrothermal plume observation. Marine Chemistry, 2001. 76(1-2): p. 17-26. Panther, J.G., et al., Titanium dioxide-based DGT technique for in situ measurement of dissolved reactive phosphorus in fresh and marine waters. Environ. Sci. Technol., 2010, 44 (24): p. 9419-9424. Panther, J.G., et al., DGT Measurement of dissolved aluminum species in waters: comparing Chelex-100 and titanium dioxide-based adsorbents. Environ. Sci. Technol., 2012, 46 (4): p. 2267-2275. Patey, M.D., et al., Determination of nitrate and phosphate in seawater at nanomolar concentrations. Trac-Trends in Analytical Chemistry, 2008. 27(2): p. 169-182. Provin, C., et al., An Integrated Microfluidic System for Manganese Anomaly Detection Based on Chemiluminescence: Description and Practical Use to Discover Hydrothermal

Plumes Near the Okinawa Trough. Ieee Journal of Oceanic Engineering, 2013. 38(1): p. 178-185. Rérolle, V.M.C., et al., Seawater-pH measurements for ocean-acidification observations. TrAC Trends in Analytical Chemistry, 2012. 40(0): p. 146-157. Rushworth, C.M., et al., Cavity-enhanced optical methods for online microfluidic analysis. Chemical Physics Letters, 2012. 554: p. 1-14. Rushworth, C.M., et al., Sensitive analysis of trace water analytes using colourimetric cavity ringdown spectroscopy. Analytical Methods, 2013. 5(1): p. 239-247. Sakamoto, C.M., K.S. Johnson, and L.J. Coletti, Improved algorithm for the computation of nitrate concentrations in seawater using an in situ ultraviolet spectrophotometer. Limnology and Oceanography-Methods, 2009. 7: p. 132-143. Sieben, V.J., et al., Microfluidic colourimetric chemical analysis system: Application to nitrite detection. Analytical Methods, 2010. 2(5): p. 484-491. Spaulding, R., M. DeGrandpre, and K. Harris, Autonomous pH and pCO(2) Measurements in Marine Environments Quantifying the Inorganic Carbon System With In-Situ SAMI Technology. Sea Technology, 2011. 52(2): p. 15-+. St. George, T., et al., A rapidly equilibrating, thin film, passive water sampler for organic contaminants; characterization and field testing. Environ. Pollut., 2011, 159: p. 481-486. Takagi, N., et al., Development of microfabricated in situ chemical analyzer. Oceans '04 Mts/Ieee Techno-Ocean '04, Vols 1- 2, Conference Proceedings, Vols. 1-4. 2004, New York: Ieee. 83-88. Tengberg, A., Jostein Hovdenes, Henrik Johan Andersson, Olivier Brocandel, Robert Diaz, David Hebert, Tony Arnerich, Christian Huber, Arne Kortzinger, Alexis Khripounoff, Francisco Rey, Christer Ronning, Jens Schimanski, Stefan Sommer, and Achim Stangelmayer. Evaluation of a lifetime-based optode to measure oxygen in aquatic systems. Limnology and oceanography, methods, 2006,4,7 -17. Todd R. Martz, Hans W. Jannasch, Kenneth S. Johnson. Determination of carbonate ion concentration and inner sphere carbonate ion pairs in seawater by ultraviolet spectrophotometric titration, Marine Chemistry, 115,4,145–154.

Vuillemin, R., et al., CHEMINI: A new in situ CHEmical MINIaturized analyzer. Deep-Sea Research Part I-Oceanographic Research Papers, 2009. 56(8): p. 1391-1399.

Walt, D.R., and Urban, E., New sensor technology for in situ measurements of ocean chemistry. Oceanography, 8, 24, 1995. Wang, Z.A., et al., Simultaneous spectrophotometric flow-through measurements of pH, carbon dioxide fugacity, and total inorganic carbon in seawater. Analytica Chimica Acta, 2007. 596(1): p. 23-36.

Appendix I

COCA working group authors

Name Institute/current Email address *Carole Barus LEGOS, France Carole.Barus@legos.obs-mip.fr Andrew Bowie University of Tasmania, Australia Andrew.Bowie@utas.edu.au Edward Boyle MIT, USA eaboyle@mit.edu

Kristen Buck Bermuda Institute of Ocean Sciences, Bermuda/University of South Florida kristenbuck@usf.edu

Hyun-Ju Cha Chungnam National University, Korea hcha80@chol.com

Petr Chocholouš Charles University of Prague, Czech Republic Petr.Chocholous@faf.cuni.cz

Mansik Choi Chungnam National University, Korea mschoi@cnu.ac.kr Helene Craigg University of Michigan, USA helenec@umich.edu Purnendu Dasgupta University of Texas at Arlington, USA dasgupta@uta.edu *Jessica Fitzsimmons MIT/Rutgers, USA jessfitz@mit.edu Martin Fleisher Lamont-Doherty Earth Observatory, USA martyq@ldeo.columbia.edu Carsten Frank Helmholtz-Zentrum Geesthacht, Germany Frank.carsten@web.de Tatsuhiro Fukuba JAMSTEC, Japan bafuk@jamstec.go.jp William Giraud CNRS, France William.Giraud@legos.obs-mip.fr *Maxime Grand University of Hawaii, USA maxime@hawaii.edu Mariko Hatta University of Hawaii, USA mhatta@hawaii.edu Gary Hieftje Indiana University, USA hieftje@indiana.edu Tung-Yuan Ho Academia Sinica, Taiwan tyho@gate.sinica.edu.tw

Burkhard Horstkotte Charles University of Prague, Czech Republic Horstkob@faf.cuni.cz

Yongming Huang Xiamen University, China yongminghuang@xmu.edu.cn Ken Johnson MBARI, USA johnson@mbari.org

Dong-Jin Kang Korea Institute of Ocean Science and Technology, Korea djocean@kiost.ac

*Corey Koch WET Labs and Seabird Scientific, USA corey@wetlabs.com Spas Kolev The University of Melbourne, Australia s.kolev@unimelb.edu.au Ilkka Lahdesmaki FIAlab Instruments, Inc., USA ilkka@flowinjection.com Maeve, Lohan University of Plymouth, UK maeve.lohan@plymouth.ac.uk George Luther University of Delaware, USA luther@udel.edu Jian Ma Xiamen University, China jma@xmu.edu.cn Graham Marshall Global FIA, USA graham@globalfia.com Chris Measures University of Hawaii, USA measures@hawaii.edu *Raquel Mesquita Universidade Católica Portuguesa, Portugal rmesquita@porto.ucp.pt

Anna Michel Woods Hole Oceanographic Institution, USA amichel@whoi.edu

*Pete Morton Florida State University, USA pmorton@fsu.edu Matt Mowlem University of Southampton, UK mcm@noc.soton.ac.uk Shuhei Nishida University of Tokyo, Japan snishida@lis.u-tokyo.ac.jp

*Hugo Oliveira REQUIMTE, ICBAS, University of Porto, Portugal hmoliveira@icbas.up.pt

Matthew Patey University of Las Palmas, Spain mpatey@gmail.com Kaitlan Prugger University of Hawaii, USA António Rangel Universidade Católica Portuguesa, Portugal arangel@porto.ucp.pt Mark Rayner CSIRO, Australia Mark.Rayner@csiro.au

Victoire Rerolle National Oceanography Centre Southampton, UK Victoire.Rerolle@noc.soton.ac.uk

Jarda Ruzicka University of Hawaii, USA jarda@flowinjection.com Kevin Schug The University of Texas at Arlington, USA kschug@uta.edu Cassie Schwanger University of Victoria, Canada cschwang11@gmail.com Kiminori Shitashima Kyushu University, Japan shita@i2cner.kyushu-u.ac.jp Steven Soper University of North Carolina, USA ssoper@unc.edu Joseph Wang UC San Diego, USA josephwang@ucsd.edu Mark Wells University of Maine, USA mlwells@maine.edu

Karen Wild-Allen CSIRO Marine & Atmospheric Research, Hobart, Australia

karen.wild-allen@csiro.au

Dongxing Yuan Xiamen University, China yuandx@xmu.edu.cn Jamie Griffith Liquid Robotics jamie.griffith@liquidr.com

*Working group rapporteur

Appendix II

Intercalibrations: To address the validation of a variety of trace element and isotope analytes, the international GEOTRACES program conducted a series of intercalibration exercises in 2008 and 2009. The results of those exercises were published in a special issue of Limnology and Oceanography: Methods in 2011-2013, which include intercalibration results and recommendations for a broad spectrum of trace elements and isotopes. GEOTRACES & SAFe http://es.ucsc.edu/~kbruland/GeotracesSaFe/kwbGeotracesSaFe.html Aerosol intercalibration: Peter L. Morton, William M. Landing, Shih-Chieh Hsu, Angela Milne, Ana M. Aguilar-Islas, Alex R. Baker, Andrew R. Bowie, Clifton S. Buck, Yuan Gao, Susan Gichuki, Meredith G. Hastings, Mariko Hatta, Anne M. Johansen, Rémi Losno, Chris Mead, Matthew D. Patey, Gretchen Swarr, Amanda Vandermark, Lauren M. Zamora Methods for the sampling and analysis of marine aerosols: results from the 2008 GEOTRACES aerosol intercalibration experiment 2013, 11:62-78 Cross-validation of methods via intercalibration exercises in recent years has resulted in significant progress being made, particularly with dissolved and particulate metals, and isotope measurements GEOTRACES IC1 (BATS) contamination-prone trace element isotopes Cd, Fe, Pb, Zn, Cu, and Mo intercalibration

Edward A. Boyle, Seth John, Wafa Abouchami, Jess F. Adkins, Yolanda Echegoyen-Sanz, Michael Ellwood, A. Russell Flegal, Kyrstin Fornace, Celine Gallon, Steve Galer, Melanie Gault-Ringold, Francois Lacan, Amandine Radic, Mark Rehkamper, Olivier Rouxel, Yoshiki Sohrin, Claudine Stirling, Claire Thompson, Derek Vance, Zichen Xue, Ye Zhao

Limnol. Oceanogr. Methods 10:653-665 (2012) | DOI: 10.4319/lom.2012.10.653

Sampling for particulate trace element determination using water sampling bottles: methodology and comparison to in situ pumps

Hélène Planquette, Robert M. Sherrell

Limnol. Oceanogr. Methods 10:367-388 (2012) | DOI: 10.4319/lom.2012.10.367

Improvements to 232-thorium, 230-thorium, and 231- protactinium analysis in seawater arising from GEOTRACES intercalibration

Maureen E. Auro, Laura F. Robinson, Andrea Burke, Louisa I. Bradtmiller, Martin Q. Fleisher, Robert F.Anderson

Limnol. Oceanogr. Methods 10:464-474 (2012) | DOI: 10.4319/lom.2012.10.464

Nutrients

Similar advances in the inter-comparability of inorganic nutrient datasets has been limited by the poor stability of nutrient solutions. However, as methodology has progressed towards achieving lower detection limits, small differences between measurements have become in some situations very significant, and the need for the widespread use of such a material has increased. Recently, progress has been made in stabilizing nutrients in seawater by techniques such as pasteurization, and it now remains to produce and distribute a set of nutrient reference materials for use in intercalibration studies and method validation.

http://dx.doi.org/10.1016/j.marchem.2011.10.002 Pasteurization: A reliable method for preservation of nutrient in seawater samples for inter-laboratory and field applications

Marine Chemistry, Volumes 128–129, 20 January 2012, Pages 57-63 Anne Daniel, Roger Kérouel, Alain Aminot