advantages of idms to the analysis of pfoa and pfos from ... · advantages of idms to the analysis...

Advantages of IDMS to the analysisof PFOA and PFOS fromenvironmental samples

Sami HuhtalaFinnish Environment Institute

2nd Nordic MS Symposium

8.11.2011

The perfluoroalkyl acids (PFAAs)

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● The perfluoroalkyl acids (PFAAs), namely perfluoroalkane sulfonic acids(PFSAs, eg. PFOS) and perfluorocarboxylic acids (PFCAs, eg. PFOA), are ubiquitous contaminantsfound in diverse environmentalcompartments.

● The attention has focused to their occurrence, effects and environmental fate thus presenting challenges to analytical work.

( R.C. Buck, J. Franklin, U. Berger, J.M. Conder, I.T. Cousins, Pimde Voogt, A.A. Jensen, K. Kannan, S.A. Mabury, S.P.J.vanLeeuwen; Integrated Environmental Assessment and Management, DOI 10.1002/ieam.258 )

Introduction

Perfluorinated compounds (PFCs) have been used in a multitude of industrialapplications and consumer products for many decades. In recent years,however, the discovery of the high environmental persistence, bioaccumulativepotential and toxic effects of some of the longer chain perfluorinatedcompounds has caused increasing concern leading to regulatory restrictions ofsome of these compounds.

Perfluorooctanoic acid (PFOA) is a commonly appearing PFC in theenvironment. It has been used particularly for manufacturingpolytetrafluoroethylene (Teflon), but it is also formed as a degradation productof several fluoropolymers and fluorotelomer alcohols that are currently used asintermediates in the manufacture of a diverse number of products includingpaints, coatings, polymers, waxes, polishes, electronics and caulks.

The objective of the present study is to investigate whether this generallypersistent pollutant is degraded photochemically in the environment. Asreported in the literature (Hori et al. 2004) PFOA has strong absorption fromthe deep UV-region to 220 nm and weak absorption from 220 nm to 270 nm.Hence, PFOA does not absorb natural sunlight (λ = 290–720 nm) and cannotbe photodegradated by direct reactions. However, natural components ofsurface water (nitrate, fulvic acid and ferric iron) are known producers ofhydroxyl radicals and can potentially mediate indirect photodegradation ofPFOA.

Here we compared photodegradation of PFOA by solar radiation-inducedindirect reactions to direct photodegradation of PFOA by artificial UV-C (254nm) radiation.

Materials and Methods

•Test solutions:

• Nordic fulvic acid (10 mg C l-1 )

• KNO3 (1 mg l-1 NO3-N )

• Fe2(SO4)3 (50 µM)

• Filtered sea water from the Gulf of Finland

• pure MilliQ-water

• PFOA to the final concentration on 100-150 ng l-1 (certified standard solution, Wellington Laboratories)

• Photochemical experiments:

•Atlas Suntest CPS+ solar simulator with irradiation times of 66 and 165 hrs corresponding to 10 and 25 days of natural sunlight

•Low pressure Mercury lamp (15 W) emitting at 254 nm wavelength, irradiation times 48 and 144 hrs

• Chemical analysis: •Solid phase extraction using C-13 labeled internal standards•The parent compound and the decomposition products were analyzed with an UPLC-ESI-MS/MS* instrument (Waters)

* ultra-high pressure liquid chromatography combined with an electron spray ionization leading into a mass spectrometer consisting of two MS units

Results

Fulvic acid (NoFA), nitrate, ferric iron and sea water have much strongerabsorption in the range of solar radiation (290-720 nm) as compared toPFOA (Fig. 1).

Degradation potential of environmentally persistent perfluorooctanoicacid (PFOA) via indirect photochemical reactions in ambient conditions

References

1. Hori H, Havakawa E, Einaga H, Kutsuna S, Koike K, Ibusuki T, Kiatagawa H, Arakawa R. 2004. Decomposition of environmentally persistent perfluorooctanoic acid in water by photochemical approaches. Environmental Science and Technology 15:6118-6124.

2. Wang Y, Zhang P, Pan G, Chen H. 2008. Ferric ion mediated photochemical decomposition of perfluorooctanoic acid (PFOA) by 254 nm UV light. Journal of Hazardous Materials 160: 181-186.

Conclusions

Solar radiation cannot decompose PFOA. PFOA half-life in theenvironment was estimated to be greater than 93 years. Therefore it isextremely important to further restrict the use of PFOA, avoid its leakageto the nature, develop the decomposition methods in the industry andsearch for environmentally degradable substitutes for PFOA.

(1 Department of Environmental SciencesUniversity of [email protected]

(2 Research and Innovation LaboratoryFinnish Environmental Institute

Sanna Vaalgamaa(1, Anssi V. Vähätalo(1, Noora Perkola(2 and Sami Huhtala(2

HY 14; valo NO3

Time1.0 0 1 .20 1 .40 1.6 0 1. 80 2 .00 2.2 0 2. 40 2 .60 2.8 0 3. 00 3 .20 3.40 3. 60 3 .80 4.00

%

0

10 0

4

3

2

1

Figure 1. UV-vis spectra of studied solutions.

Figure 2. The concentration of PFOA in the solar irradiation experiments.

Figure 3. Photodegradation of PFOA by 254 nm UV-C light.

The samples irradiated with UV-C radiation showed clear peaks ofperfluoroheptanoic and perfluorohexanoic acids suggesting that the PFOAwas (sequentially) degraded via decarboxylation (Fig. 3). In contrary toprevious findings (Wang et al. 2008) ferric ion did not seemingly enhancethe decomposition and defluorination of PFOA. The amount ofdecomposition products was greatest in the reaction solution containingpurified water (Fig. 4). This is suggested to be caused by shading effect offulvic acid and ferric sulphate.

Figure 3. PFOA and its decomposition intermediates of UV-C irradiated NO3

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solution. The peaks are 1= perfluoropentanoic acid (PFPeA), 2=perfluorohexanoic acid (PFHxA), 3= perfluoroheptanoic acid (PFHpA), 4=perfluorooctanoic acid (PFOA ).

UVC treatm ent NO3-

0 24 48 72 96 120 144

t (hrs )

0

25

50

75

100

ng

/l

0 24 48 72 96 1 20 144

t ( hrs)

0

25

50

75

100

ng

/l

UVC treatment MilliQ

PFOA

PFHpA

PFHxA

UVC treatment N oFA

0 24 48 72 96 12 0 144

t (hrs)

0

25

50

75

100

125

ng/

l

UVC trea tment Fe(III )

0 24 4 8 72 96 120 144

t (hrs )

0

2 5

5 0

7 5

10 0

ng

/l

UVC trea tment SW

0 24 48 72 96 1 20 144

t (hrs)

0

25

50

75

100

ng/

l

No decline in the PFOA concentration (Fig. 2) nor emergence of thedecomposition products were observed in the irradiated (UV-Vis)samples.

Research on PFAAs in SYKE


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● Used widely in carpets, textiles, leather and paper to enhance resistance to water and dirt

● Also used in cleaning fluids, floor waxing products, in photography and industrial processes for mist suppression.

● PFOA is a one component of Teflon

● PAPs (polyfluorinated alkyl phosphates) are likely to release PFOA as degradation product


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● WWF 2004: European Ministers of Environment blood samples weretested for common contaminants.

● At that time the Minister of Environment in Finland was Jan-Erik Enestam. His blood sample contained 38 different chemicals.


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● PFAA concentrations in Finnish River Waters, Waste Water Effluents and Sludge samples

(Units: ng/L , µg/kg)

Information about hazardous substances in the Baltic Sea region (COHIBA) www.cohiba-project.net

● The use of isotope dilution mass spectrometry (IDMS) has become more common with the increase of mass spectrometric instrumentation and applications.

● IDMS was introduces in organic chemistry in the 1970s. (Pickup J.F., McPherson K., Anal. Chem., 48, 1885-1890, 1976)

● The instrument (MS) response varies because of many different reasons, internal standards are needed.

● The isotopically labelled standard compound resembles the analyte and it is separated from the analyte by it´s higher mass.

● The isotope labels are commonly 13C or deuterium

● Also the availlablity of labeled standards has increased. But… they are still rather expensive.

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Isotope dilution mass spectrometry (IDMS)

● IDMS enhances the accuracy of measurements, especially in difficult sample matrix:

○ Compensation of possible errors made during samplepretreatment is accurate because of the ´identical´behaviour of analyte and isotopically labelled istdcompound.

○ Precise determination of recovery -%

○ Verification of retention time (also usage of RRT)

○ Information of ionisation processes (eg. adductformation, ion suppression)

● IDMS simplyfyes the data handling and number cruntcingspecially in organic chemistry

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n

isample m

cc =

s

i

s

i

c

c

A

A=

● The used isotopically labelled standards should be selectedwith care:

○ The relative MW of the internal standard should be at least three mass units higher.

○ Natural isotopes may cause overlapping of measuredsignals (eg. higher brominated compounds)

○ Deuterated compounds do behave differently

(eg. rt, adduct formation, isotopic exchange D -> H)

● The isotopically labelled standards should be used carefully:

○ Gravimetric dilutions

○ Accurate additions (pipette accuracy, addition volume)

○ Stability, storage, …

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● However…

The nomenclature of internal standard solutions is inconsistent and the purpose of the internal standard is not always readily apparent.

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Terms and applications of internals standards

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Internal standard A compound added to a sample in known concentration to facilitate the qualitative identification and/or quantitative determination of the sample components (IUPAC)

Surrogate

(Other terms: Recovery standard, Extraction standard)

In our study(13C2PFHxA, 13C4 PFOA, 13C4 PFOS and 13C2PFDA, 50 ng mL-1)

To quantificate the analytesTo evaluate recovery (extraction, clean up)

Instrument standard

(Other terms: Performance standard, Injection standard

In our study(13C8-PFOS and 13C8-PFOA,25 ng mL-1)

To calculate recovery of surrogate standard

Sample Pretreatment

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● Analytes were extracted by Oasis HLB SPE cartridges.

● Prior to SPE, surrogate standards and 0.1 mLNH4OAc were added to the samples.

● The analytes were eluted with MeOH.

● 0.3 mL of extract was transferred to a PP vial, and 0.7 mL of Milli-Q water and instrument standards were added.

● Analysis by UPLC - TQ MS

Instrumentation for PFC analysis:

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● Waters Acquity UPLC

● Column system:○ PCF – Kit ○Van Guard Pre-Column:

Acquity UPLC BEH C18 1.7µm 2.1 x 5mm○ Analytical column:○ Acquity UPLC BEH C18 1.7µm 2.1 x 50mm

● Waters Xevo TQ MS○ ElectroSpray Ion source, Negative

● Oil free Scroll Pump

Instrumentation for PFC analysis:

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PFC Kit:

● PEEK solvent lines

● Special solvent filters

● Isolator column:

○UPLC BEH C18 2.1 x 50 mm

○ Installed between solvent mixer and sample valve to delay signals originating from the instrument

Experiment

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● To study the effect of IDMS three different water samples (Milli-Q water, natural water and waste water) were spiked at low level and high level concentrations.

● Samples were analysed as four replicate measurements

● Analysis were repeated three times on different days.

● The calculations of PFOA and PFOS concentrations are done varying the functions of applied mass labeled internal standards

Results: PFOS

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Results: PFOA

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Results: Overview

● The within-day variation were higher than expected. Explanation for this could be that too lowconcentration and/or addition volume of ISTDs were used.

● STDs as well as deviation from ref. value with other ISTD variations were larger at PFOS data than at PFOA data. Thus PFOA is more sensitive to the used surrogate compound than PFOS.

● The longer chain mass labelled surrogate standard (PFDA) gave significantly higher results for both PFOA and PFOS than analog or shorter chain (PFHxA) standards.

● The differences (deviation from reference value, variation of results) were larger at lower concentrations.

● The more difficult sample matrix is the bigger are the differences in the results.The differences in sludge results were 3-5 times higher than in water sample results when non-identical standards were employed.

● Quantification with surrogate standards give readily recovery corrected results

Conclutions● The usage of isotopically labelled internal standards

improves the quality of analytical results in water samples. ● It is recommended to use isotope labeled internal standards

(analog to the analyte) as surrogates when possible. ● Specially for the analysis of water samples 13C standards

are recommended● The purpose that internal standards are used for should be

reported when publishing quantitative data to make the data more comparable.

● The benefits achieved with the correct application of mass labeled internal standards are clear: data handling is simplified, the accuracy and the quality of reported results are increased.

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Thank you for attention !Thank you for attention !

MS/MS method● MRM transitions for the PFSAs:

[M-H]- → FSO3-

[M-H]- → SO3-. (-> 99)

The latter one was found to be non-specific and exhibited false positive findings

● MRM transitions for the PFCAs:[M-H]- → [M-H-COO]-[M-H]- → [M-H-COO-(CF2)x]-.Both transitions were found to be specific for PFCAs.

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MS/MS method● Acquity UPLC - TQ MS Xevo (Waters, USA) using ESI- and MRM

mode● A PFC isolator column was placed before the injection valve to

delay signals originating from the instrument.● Acquity UPLC® BEH C18 column (1.7 µm x 2.1 mm x 50 mm) at

temperature of 60 oC. Injection volume 5 µl was used.● Mobile phase consisting of methanol (2 mM NH4OAc) and water

(2 mM NH4OAc) at flow rate of 0.6 ml min-1

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