MICROWAVE-ASSISTED EXTRACTION COUPLED WITH GAS-CHROMATOGRAPHY ELECTRON-CAPTURE NEGATIVE CHEMICAL-IONIZATION MASS-SPECTROMETRY FOR THE SIMPLIFIED DETERMINATION OF IMIDAZOLINONE HERBICIDES IN SOIL AT THE PPB LEVEL

The imidazolinones are a significant new class of low-use-rate, reduce d-environmentaI-risk herbicides for protection of a wide variety of ag ricultural commodities, Because of their low rates of application, res idues of the imidazolinones in soil need to be monitored at the low pp b level, Current methodology for this purpose involves an exhaustive b ase extraction followed by a laborious, time-consuming cleanup procedu re to permit analysis at the 5 ppb level. Using imazethapyr, the most widely utilized member of the class, as a representative, we have achi eved not only a limit of quantitation of 1 ppb but also a greatly simp lified cleanup procedure by combining microwave-assisted extraction te chnology with gas chromatography/electron electron capture negative ch emical ionization mass spectrometry, On a variety of soil types coveri ng a fortification range of 1-50 ppb, an average recovery of 92% with a standard deviation of 13% was achieved. Control soil extracts gave a pparent residues of <0.2 ppb, Sample preparation time per sample was r educed from 2 h to 10 min.