FULLY AUTOMATED MULTI-RESIDUE METHOD FOR TRACE-LEVEL MONITORING OF POLAR PESTICIDES BY LIQUID-CHROMATOGRAPHY

A fully automated liquid chromatographic method using on-line trace enrichment, gradient elution and diode-array detection for the trace level determination of polar pesticides in surface water is described. The automated system uses specially developed software in the form of ''user macros'', allowing the on-line control of both the automated cartridge exchange unit for sample preparation and the liquid chromatograph with diode-array detector by means of the Pascal Workstation computer of that liquid chromatographic system. The collected data are automatedly evaluated, i.e., pollutants present in the sample at a concentration level above an input treshold level are identified/determined and a report is printed. Parameters such as the sampling interval of the spectra, temperature of the analytical column compartment, wavelength/bandwidth ratios and data handling were optimized. The validation results for 27 pesticides are presented. At an analyte concentration of 1 mug/l the relative standard deviations of the retention times and peak areas in different types of water are in the range 0.2-1.5% and 1-15%, respectively. All calibration graphs are linear in the range 0.1-7 mug/l.