Analysis of metsulfuron-methyl in soil by liquid chromatography/tandem mass spectrometry. Application to a field dissipation study

An analytical method is described for the extraction of metsulfuron-methyl from soil at sub-parts per billion levels (LOQ = 0.2 mu g kg(-1)). The herb icide was quantitatively determined and identified by ESI LC/MS/MS. The met hod has been applied to a field dissipation study in which metsulfuron-meth yl was applied to spring barley at three dosage rates: 4, 8, and 16 g of ac tive ingredient ha(-1) The results of 2 years are presented. The dissipatio n rate of metsulfuron-methyl in topsoil was very rapid, with a calculated h alf-life of 6.5 days. Laboratory mineralization studies with native soils i n contrast to autoclaved soils indicated that microbial degradation of C-14 -labeled metsulfuron-methyl and C-14-labeled 2-amino-4-methoxyl-6-methyl-1, 3,5-triazine soil microcosms is an important factor for the complete degrad ation of metsulfuron-methyl in the field. However, the mineralization rate of the sulfonamide was much higher.