Determination of carbendazim and thiabendazole in environmental water samples using solid-phase extraction and LC/electrospray MS/MS

Carbendazim (MBC) and thiabendazole (TBZ) in environmental water samples were simultaneously determined by a liquid chromatograph/tandem mass spectrometer equipped with an electrospray ionization interface (LC/ESI-MS/MS). A simple and rapid sample pretreatment procedure using solid-phase extraction was developed to minimize the ion-suppression effect and to enrich analyte compounds. Both MBC and TBZ were quantitatively retained on a solid-phase extraction cartridge (Oasis HLB). The cartridge was washed with 3 ml of a 30 vol% methanol solution and then with 3 ml of water, and subsequently dried under a vacuum. MBC and TBZ retained on the cartridge were recovered by elution with 4 ml of ethyl acetate. The eluate was taken to dryness under a nitrogen stream before being re-dissolved in 1 ml of a water/methanol (1 : 1) solution. The solution was analyzed by LC/ESI-MS/MS. The results of analyses of spiked MBC and TBZ in aqueous solution demonstrate the applicability of the proposed method to environmental aqueous solutions, such as river water and the discharge of sewage treatment plant (DSTP). Detection limits of 0.32 ng/1 for MBC and 0.93 ng/1 for TBZ in river water, and 5.6 ng/1 for MBC and 4.9 ng/1 for TBZ in DSTP have been achieved. The results of overall recovery tests showed that the recovery of deuterated MBC-d(3), the spiked internal standard, was 85.4%, and that the relative standard deviation (RSD) was 11%. The recoveries of MBC for river water spiked at 5 ng/1 and 50 ng/1 were 102% and 104%, and for DSTP spiked at 250 ng/1 was 106%, respectively, and their RSD ranged from 1.9% to 3.4%. The recoveries and RSD of TBZ ranged from 78.9% to 136%, and from 1.8% to 4.8%, respectively.