Field Methods of Monitoring Aquatic Systems Unit 9 – Ion-Chromatography Copyright © 2006 by DBS

Suppressed IC System Chromographic separation of inorganic anions –Provides analysis of many ions at once –Organic polymer column (10-25 cm, 3-5 mm ID) and CO 3 2- /HCO 3 - elluent Detection via conductivity –Eluent ions must be removed (background conductivity) (Na + replaced by H +, CO 3 2- /HCO 3 - converted to CO 2 ) –Suppresor removes all buffer ions via ion exchange or continuous suppression) electolysis Eluent reservoir Pump Analytical column Ion Supressor Conductivity detector Injection system

Chromatographic Separation Principles 1. Mobile phase – eluent carries the mixture through the column 2. Stationary phase – compounds adsorb to ion-exhcange resin in the column. Stickier compounds require more elution time 3. Force pushes the mixture through the column – pump 4. Separation depends on retention time (ion charge and size) Column is covered in +ve binding sites - N(CH 3 ) 3 + As sample passes over the resin, anions in the sample replace bicarbonate ions bound to the resin [Resin] + -HCO 3 - +Cl - [Resin] + -Cl - + HCO 3 - Eventually sample anions are displaced again by new eluent (bicarbonate) and washed off the column

Kegley, 1998

IC Chart Conductivity Conductivity ~ concentration Compare peak area of unknown with that of a standard

Procedure In environmental waters samples require filtration (0.45 μm) Standardization 1.Inject standards one at a time to obtain peak areas at different concentrations 2.Plot concentration vs. peak area for each component and obtain a calibration graph for each component Sample Run 1.Inject the filtered sample and use the calibration for each ion to obtain concentrations of anions 2.If anion peaks go off-scale dilute the sample using pipets and volumetric flask. 3.Determine concentrations in mol L -1 and ppm. 4.Determine total moles of negative charge.

Dionex ICS-1000 Chromeleon software Continuous electrolytic suppression

Question Use the following data to draw a calibration curve and calculate the concentration of the sample. 12 ppm

Procedure Pump window –0.1 mL normal flow, increase to program flow (e.g. 1.2 mL for SO 4 2- ) Anion.qnt –Adjust file –Check 10 mM CO 3 2- /1 mM HCO 3 2- Batch –Must be run on samples (add to batch) Peak assignment –Assign retention times to peaks in software

Text Books Rump, H.H. (2000) Laboratory Manual for the Examination of Water, Waste Water and Soil. Wiley-VCH. Nollet, L.M. and Nollet, M.L. (2000) Handbook of Water Analysis. Marcel Dekker. Keith, L.H. and Keith, K.H. (1996) Compilation of Epa's Sampling and Analysis Methods. CRC Press. Van der Leeden, F., Troise, F.L., and Todd, D.K. (1991) The Water Encyclopedia. Lewis Publishers. Kegley, S.E. and Andrews, J. (1998) The Chemistry of Water. University Science Books. Narayanan, P. (2003) Analysis of environmental pollutants : principles and quantitative methods. Taylor & Francis. Reeve, R.N. (2002) Introduction to environmental analysis. Wiley. Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., eds. (1998) Standard Methods for the Examination of Water and Wastewater, 20th Edition. Published by American Public Health Association, American Water Works Association and Water Environment Federation.