Analysis of phenylurea herbicides in groundwater by reversed phase capillary electrochromatography

A reverse phase capillary electrochromatographic method in combination with solid phase extraction on octadecyl-silica cartridges was optimized for the analysis of phenylurea herbicides at ppt concentration level in groundwater environmental samples. The optimum experimental conditions were found after evaluating several physico-chemical parameters affecting the analytes separation, as e.g., the mobile phase organic solvents content and composition, the buffer concentration and pH, the analytes injection times. The method allowed to determine phenylurea herbicides in groundwater at concentration of 50 ppt (each herbicides unextracted concentration) using 5 mM MES buffer pH 5.0 65% acetonitrile 5% methanol as mobile phase. The method was repeatable and linear in the range 1-2.5 mg×mL-1 (injected analytes concentrations). The analysis of extracted groundwater samples from different wells detected the phenylureas in interference free electrochromatograms in less than 9 min at 50 and 100 ppt level (unextracted sample concentration). Different sample matrices seemed to not affect the optimized method.