Simultaneous Determination of Iminoctadine, Diquat, and Paraquat in Tap and River Water by Liquid Chromatography-Tandem Mass Spectrometry after Solid-Phase Extraction

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 offi cial 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 fl ow 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 coeffi cients 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 .