Determination of quats in beverages and urine samples by capillary zone eletrophoresis

Conditions have been developed for simultaneous determination of paraquat (PQ) and diquat (DQ) by capillary zone electrophoresis (CZE) with diode array detector (DAD) after their preconcentration by solid phase extraction using Megabond Elut C18 and Strata X 33 μm Polymeric sorbent cartridges. Conditions were optimised with reference to pH, EDTA concentration in sodium acetate acetic acid buffer of pH (3.8) with 3-8% of methanol, ethanol and acetonitrile as organic modifier in the background electrolyte. UV detection with variable wavelength was used to determine each compound at its maximum absorption providing an excellent sensitivity. The recovery of these compounds from water samples spiked at different levels was more than 90%. The limit of detection (S/N=3) obtained for milli-Q water when spiked with standards was 0.17 ppm for DQ and 0.19 ppm for PQ, in tap water samples it was found to be 0.27 ppm for DQ and 0.31 ppm for PQ, in cola beverages it was found to be 0.29 ppm for DQ and 0.35 ppm for PQ, and for the urine samples it was 0.36 ppm for diquat and 0.41 ppm for the PQ without preconcentration. After preconcentration using polymeric cartridge the detection limit was reduced to 2.5 ppb for DQand 3 ppb for PQ for the milli-Q water. These detection limits allows for the analysis of these compounds at the levels established by the US Environmental Protection agency.