Comparison of capillary electrophoresis and liquid chromatography for determination of sulfonylurea herbicides in soil

Two analytical methods developed for degradation studies in soil were compared for the simultaneous determination of sulfonylurea herbicides. The compounds were extracted with phosphate buffer from soil samples after purification and enrichment steps by solid-phase extraction. Samples were analyzed by liquid chromatography (LC) or capillary electrophoresis (CE) with UV detection. Amidosulfuron, bensulfuron-methyl, chlorimuron-ethyl, chlorsulfuron, ethametsulfuron-methyl, metsulfuron-methyl, nicosulfuron, primisulfuron-methyl, sulfometuron-methyl, thifensulfuron-methyl, triasulfuron, and tribenuron-methyl were separated within 90 and 35 min by LC and CE, respectively. Average recoveries, determined with LC for 5 sulfonylureas in 1-100 mu g/kg soil ranged from 74 to 103%, and those determined with CE for 10 sulfonylureas in 2-20 mu g/kg soil ranged from 87 to 105%. Bensulfuron-methyl was recovered at lower levels of 52%. The limits of quantitation were 1.0 and 2.0 mu g/kg soil for LC and CE, respectively, Coefficients of variation were higher for CE than for LC. Although both methods are suitable, the LC method, which is more sensitive and accurate than the CE method, is preferred for field studies. However, CE, which was shown to be faster with lower operating costs and unlimited repeatability of the analysis due to little injection volumes, is preferred for laboratory studies.