Abstract
The pesticide list for drinking water in Japan was revised on March 28, 2013, and the herbicide paraquat was listed as a target pesticide. However, no official analytical method for paraquat has been established by the Ministry of Health, Labour and Welfare in Japan. We investigated an analytical method for the simultaneous determination of paraquat, diquat, and iminoctadine in water with liquid chromatography-tandem mass spectrometry after solid-phase extraction (SPE). The optimum sample volume and flow rate in SPE, using a mix-mode cartridge that has reverse-phase and weak cation-exchange modes, were 20 mL and 1-2 mL·min-1, respectively. The adsorption of iminoctadine onto the SPE cartridge was not affected by pH or the concentrations of Na, K, Ca, and Mg cations in the water sample, whereas those of diquat and paraquat were affected by these factors. The recoveries and coefficients of variation of the three pesticides were 78-127% and 4.4-6.1%, respectively, in tap water at the spiked pesticides concentration of 0.05 μg·L-1.
