Time-of-flight high resolution versus triple quadrupole tandem mass spectrometry for the analysis of quaternary ammonium herbicides in drinking water

Conditions for the simultaneous determination of quaternary ammonium herbicides by liquid chromatography–electrospray–mass spectrometry were established. Two electrospray sources with different configurations and two mass analyzers were used: a Turbo Ionspray™ source with a triple quadrupole instrument and a Z-spray source with a time-of-flight (TOF) analyzer. The separation was performed using ion pair reversed phase chromatography. An on-line solid-phase extraction procedure with polydivinylbenzene cartridges was automatized by using a Prospekt device coupled to both LC–MS instruments. Good run-to-run precisions were obtained for both instruments, and the determination of quats in drinking water was evaluated using spiked samples. Better limits of detection were obtained using tandem mass spectrometry. The results obtained allowed the analysis of quats in drinking water samples below the legislated levels.