ABSTRACT
Over 2 weeks of cartridge storage, no significant analyte loss was observed when the sample was kept frozen as a precaution. Comparing this method with one using a C18 extraction cartridge, the former appeared to be superior to the latter in terms of sensitivity and, chiefly, of selectivity. This method involves confirmatory analysis by LC-ESI-MS instrumentation equipped with a single-quadrupole mass filter. MS data acquisition was performed by a timescheduled three-ion SIM program. The necessary structure-signficant fragment ions were obtained by controlled decomposition of SU adducts ions after suitably adjusting the electrical field in the desolvation chamber. Under the three-ion SIM condition, limits of detection calculated from the ion current profiles of those fragment or parent ions giving the lowest signal-to-noise values ranged between 0.5 (tribenuron methyl) and 3 ng (metsulfuron methyl, thifensulfuron methyl) injected into the LC column.
