Ion-trap versus quadrupole for analysis of quaternary ammonium herbicides by LC-MS

An ion-trap mass spectrometer for determination of quaternary ammonium herbicides in water samples is evaluated. Implementation of the method previously optimized in a quadrupole mass spectrometer (VG Platform ii) in an ion-trap (LCQ) required modifications to the sample inlet of the electrospray source. Quality parameters were established and detection limits, after trace enrichment, ranged 5 - 50 ng L-1. Good reproducibilities (day-to-day and run-to-run) < 12% were obtained. The method was applied to analysis of spiked samples and the results were comparable with those determined using a quadrupole mass spectrometer.