Simultaneous Determination of 11 Neonicotinoid Pesticides in Domestic Drinking Water by HPLC-MS/MS with QuEChERS

A method for the simultaneous determination 11 neonicotionid pesticides, including imidacloprid, nitenpyram, acetamiprid, thiacloprid, imidaclothiz, cycloxaprid, thiamethoxam, clothianidin, dinotefuran, sulfoxaflor and flonicamid in domestic drinking water by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) with QuEChERS was proposed. The filtered water sample (5 mL) was extracted twice with dichloromethane solution containing 1% (volume fraction) formic acid. Then the lower extract solutions were combined and blown to dryness by nitrogen, and 50 mg of N-propyl ethylenediamine (PSA) and 1 mL of the mixed solution composed of 0.2% (volume fraction, the same below) formic acid solution and acetonitrile at volume ratio of 65\:35 were added. After vortex, the above solution was passed through 0.22 μm polyether sulfone filter membrane. The mixed solutions composed of 0.2% formic acid solution and acetonitrile at different volume ratios were used as the mobile phase for gradient elution. The separated 11 targets were scanned by electrospray ion source with positive ion mode, detected by multiple reaction monitoring mode, and quantified by external standard method. As shown by the results, linear relationships between the mass concentrations and corresponding peak areas of 11 neonicotionid pesticides were kept in definite ranges, with lower limits of determination (10S/N) in the range of 0.02-0.08 μg·L^-1. The recoveries of 11 targets were in the range of 62.1%-101% at 3 spiked concentration levels, and RSDs (n=6) of the determined values ranged from 5.0% to 15%. The method was applied to analysis of 8 samples of tap water, 4 samples of river water and 3 samples of reservoir water. It was shown that neonicotionid pesticides including clothianidin, imidacloprid, thiamethoxam and acetamidine were deteceted in 4 samples of river water and 2 samples of reservoir water, and the other samples were not detected targets.