Analytical Chemistry of River Water- an undergraduate laboratory projectDr R. J. Ansell, S. Abd Kudus, C. Bleasdale, M. Cullen, D. Fogarty, K. Hardman, W. Heath, G. Hesson, C. Scott & D. ThompsonSchool of Chemistry, University of Leeds, UK

RationaleWater analysis provides a range of possibilities for teaching Analytical Chemistry in an applied context within the laboratory1,2. In the current project, students compared different analytical techniques for the measurements of specific anions, cations and organic pollutants in river water (and tap water). Level 3 Chemistry with Analytical Chemistry students worked in pairs, spending 3 weeks working on each class of analytes. Water was collected at 3 points in the year and the students rotated so that they had the opportunity to look at all 3 classes of analytes over the year. Students were not given detailed instructions but were required to investigate alternative analytical methods for themselves, using equipment currently available in the School of Chemistry teaching laboratories. For each analyte two different methods were compared. The project was thus intended as an antidote to more traditional laboratory experiments where the samples, instructions and end-point of the experiment are given (Domin writes 'Just as a catalyst speeds up a chemical reaction by providing an alternative lower energy pathway, the laboratory manual reduces the amount of time necessary to complete a laboratory activity by providing an instructional pathway that does not require the utilization of higher-order thinking skills’3). Within the project, students were required to engage with research and learn research skills, including presenting their findings in the format of a research paper.

Results - Cations

Results - Anions

Results - Pesticides

ConclusionsA range of new analytical methods were introduced to the students (and to the project manager!) which - Improved the understanding of material previously taught in lectures- Required students to investigate, plan and adapt experiments for themselves, with

guidance but without a fixed ‘recipe’- Yielded results that could not be predicted, and provided a context for students to

consider accuracy, precision and significance of their data- Gave students a taste of researchStudents were fully engaged with the project, some requesting to be allowed to do extra lab-work outside of lab hours, and the marks reflected this enthusiasm (between 64 and 87%).The results provide a useful overview of the chemistry of West Yorkshire’s rivers.

References and Acknowledgements1. R.J. Arnold, ‘The water project: A multi-week laboratory project for undergraduate analytical chemistry’, Journal of Chemical Education, 2003, 80, 58-602.G. Adami, ‘A new project-based lab for undergraduate environmental and analytical chemistry’, Journal of Chemical Education, 2006, 83, 253-2563. D.S. Domin, ‘A content analysis of general chemistry laboratory manuals for evidence of higher-order cognitive tasks’, Journal of Chemical Education, 1999, 76, 109-111.4. The River Restoration Centre, http://www.therrc.co.uk/J. Donkin, N. Howes and M. McMullon are acknowledged for help designing and testing the project and I. Blakeley is thanked for assistance with the atomic absorption measurements. D. Preston (Environment Agency), V. Hirst and P. Kay are acknowledged for their help in identifying sampling sites and candidate pesticides for testing. RJA is grateful to the University of Leeds for a Teaching Fellowship which made the project development possible.

SamplingSamples were collected from sites on four rivers in West Yorkshire, representing catchments with differing geologies and levels of industrial / agricultural activity. Three of the sites used are also used by the Environment Agency for water quality monitoring.

Rivers map from RRC4

All the tests were completed successfully by one or more pairs of students, except the pyrocatechol violet assay for aluminium. The amount of lead in all the water samples was undetectable by AA and near the limit of the kit assay. There were significant differences between measurements on samples collected at different times, between samples from the different rivers, and between measurements with the two different techniques. The latter provided a context for the students to consider the relative accuracy and precision of different methods.

Tap water River Aire River Calder River Colne River Wharfe Oct-

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H+ (pH) Palintest PM130 kit assay 7.5 7.6 7.5 8.1 7.6 8 7.8 6.8 7.2 7.6 7.3 6.5 8.4 8.2 8 pH electrode (EPA method 150.1) 7.2 7.1 7.1 7.8 7.2 6.9 7.5 6.6 6.8 7.2 6.6 6.8 8.2 7.5 7.3Iron (mg/L) Hanna HI3834 kit assay 0 0 <1 0.75 1 1.25 <1 1.25 1 0.5 Atomic absorption (UK SCA Method 1983) 0.003 0.08 0.02 0.15 0.06 0.27 0.11 0.36 0.03 0.19Calcium (mg/L) Palintest PM 252 kit assay (Calcicol) 76 100 20 69 Titration (EPA method 215.2 ) 75 139 35 12 75Lead (mg/L) Merck Spectroquant 1097170001 kit assay <0.1 <0.1 <0.1 <0.1 <0.1 Atomic absorption (EPA method 239.2) 0 0 0 0 0 Aluminium (mg/L) Palintest PM 166 kit assay 0.02 0.06 0.05 0.09 0.04 0.12 0.25 0.08 0.08 0.30 0.09 0.28 0.24 0.03 0.14 pyrocatechol violet assay (UK SCA Method 1987)

Tap water River Aire River Calder River Colne River Wharfe Oct-

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Carbonate (mg/L) Palintest PM188 kit assay (Alkaphot) 67 0 213 108 63 0 77 0 218 8 Titration (EPA method 310.1) 68 46 161 120 51 23 21 8 160 69Nitrate (mg/L) Hannah Instruments HI-3874 assay (Cd, colorimetric) 0.2 1.2 1.2 1.3 0.1 Jenway WAT-120-540K assay (chromotropic acid) 2.8 3.0 2.4 0.5 1.0 Colorimetric, brucine (EPA method 352.1) 0.7 1.8 0.9 2.5 0.8 0.8 0 0 0 0.1Sulphate (mg/L) Jenway Aquanova 025 334 kit assay 70 64 114 62 38 28 76 9 17 4 Gravimetric (EPA method 375.3) 57 31 87 39 51 18 61 3 9 21Phosphate (mg/L) Palintest PM177 kit assay 2.0 3.0 0.4 0.4 0.3 Colorimetric SnCl2 (US Standard Method 4500-P D) 2.5 4 0.6 0.7 0.7 Fluoride (mg/L) Thermo Orion Aquafast AC2009 assay (SPADNS) 0.2 0 0.3 0.2 0.2 Ion selective electrode (EPA method 340.2) 0.4 0.4 0.3 0.6 0.9 1.0 0.3 0 0.5 0.5

All the tests were completed successfully by one or more pairs of students, although fluoride and nitrate were close to the limits of detection (three different methods for nitrate were investigated). There were again significant differences between samples collected at different times, between samples from the different rivers, and between measurements using the two different techniques. The Aire and Wharfe samples contained most carbonate, as well as most calcium, consistent with the limestone geology of their catchments.

Samples were analysed using US Geological Survey Method O-1131-95.- 1L samples filtered and passed through Carbopak-B solid phase

extraction cartridges- Bound species eluted using base-neutral eluent (DCM/MeOH)

and acid eluent (same, with 0.2% TFA)- Separate HPLC runs were performed with different mobile

phase gradients for the base-neutral and acid fractions (Inertisil ODS-3V 250x4.6 mm column, 40°C, MeCN/MeOH/TFA(aq, 0.05% v/v) gradient elution at 0.8 mL/min)

- Chromatograms were compared against standards recorded for 12 pesticides that are of national concern and/or have previously been detected in local rivers

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Chromatograms showed a range of organic compounds present at low levels. Many could not be identified on the basis of tR.Peak X (tR=47 min) had a retention time very close to the 2,4-D standard. Spiking with 2,4-D suggested this probably is the compound, and a standard addition calculation suggested an initial concentration in the Colne sample of 0.1 mg/L, which corresponds to the recommended limit.Other organic compounds were detected in the base-neutral eluted fractions, and in the January and February samples, but their identification was more tentative.

Chromatograms for acid-eluted fractions, November samples

River Wharfe, Pool-in-Wharfedale SE245455

River Aire, Allerton Bywater SE417274

River Calder, Battyeford, Mirfield SE189204

River Colne, Milnsbridge SE116159