DETERMINATION OF PHOSPHATE IN NATURAL-WATERS BY CAPILLARY ELECTROPHORESIS - INFLUENCE OF SOLUTION COMPOSITION ON MIGRATION TIME AND RESPONSE

This paper deals with the determination of the more complex phosphate anion by capillary electrophoresis using indirect UV detection. First, the pH of the running electrolyte influences both the migration time and the response of the phosphate anion. Both effects could be explain ed well by taking into account phosphorus speciation in solution. In a ddition, the experimental method has been applied to three different s ets of natural water systems; (i) groundwater, (ii) surface water and (iii) stemflow samples. The migration time behaviour of phosphate was different for the three sample sets and, hence, difficulties arise wit h respect to a clear and unique identification of the compound. Deviat ions herein could be minimized by applying a correction method for mig ration time drift. Concentrations of phosphate could be quantified in most samples and were confirmed by a colorimetric method. Average reco veries of additions of phosphate to groundwater, surface water and ste mflow samples were 105, 83 and 103%, respectively. For one stemflow sa mple, quantitative recovery of phosphate was possible only by changing the pH of the running electrolyte solution. The latter observation mi ght be very useful in setting up speciation-related measurement method s.