Multi-residue screening method of acidic pesticides in agricultural products by liquid chromatography/time of flight mass spectrometry

Abstract

A simple and rapid screening method of 95 acidic pesticides in agricultural products was developed. As acidic pesticides adsorb on the primary secondary amine mini-column with fatty acids which become interfering peaks during GC/MS analysis, they were not included in multi-residue analysis entailing PSA clean-up. In this study, the intermediate extracted solutions before PSA clean-up were analyzed by LC/TOF-MS. Accurate mass measurement of TOF-MS enabled the detection of molecular ions and fragment ions with high selectivity. Mean recoveries of 95 pesticides added to 6 agricultural products at 0.1 mg/g were 49-127% with RSD Ͻ20%. Limits of quantitation were 0.01-0.02 mg/g for 95 pesticides. The method was applied to 140 samples, and 2,4-D from lemon and orange, fluazifop from baby kidney bean, dichlorprop from apple were detected, respectively, at 0.02-0.03 mg/g below MRLs. The proposed method showed good sensitivity for 95 acidic pesticides and enabled rapid screening in combination with our multi-residue method targeted to 520 pesticides.

Pesticide residues in domestic agricultural products monitored in Hyogo Prefecture, Japan, FY 1995-2009

“…Limits of quantitation defined by the signal-to-noise ratio (S/NՆ10) were set at 0.01 mg/g for most pesticides, except for 0.02 mg/g for barban, isoxaflutole, toriforine, mesotrione, etc. 10) Limits of detection were 0.001-0.007 mg/g, and the trace level indicated that remains from 0.001 to 0.01 mg/g could be confirmed.…”

“…Analytical conditions were the same as those reported previously for GC-MS, 5,14) LC-MS 15) and LC-TOF-MS. 10) All data were acquired in SCAN mode, and the detected pesticides were confirmed by their mass spectra, and then determined by the peak area of target ion chromatograms. Limits of quantitation defined by the signal-to-noise ratio (S/NՆ10) were set at 0.01 mg/g for most pesticides, except for 0.02 mg/g for barban, isoxaflutole, toriforine, mesotrione, etc.…”

“…According to the procedure previously reported, [8][9][10] about 500 g sample was chopped in a MK-K58 food processor (Panasonic, Japan) for more than 1 min to obtain thoroughly mixed homogenates. Then, 25 g portions of chopped samples were extracted with 60 ml acetonitrile and cleaned up with ODS and a PSA mini-column for multi-residue analysis of 520 pesticides by GC-MS and LC-MS. 14,15) For 95 acidic pesticides, portions were divided before PSA purification and analyzed by LC-TOF-MS. 10) Results and Discussion…”

“…Then, 25 g portions of chopped samples were extracted with 60 ml acetonitrile and cleaned up with ODS and a PSA mini-column for multi-residue analysis of 520 pesticides by GC-MS and LC-MS. 14,15) For 95 acidic pesticides, portions were divided before PSA purification and analyzed by LC-TOF-MS. 10) Results and Discussion…”

“…We previously reported the residue results before the Positive List System, [5][6][7] and subsequently markedly increased the number of pesticides to more than 440 analyzed by the multi-residue method. [8][9][10] Residue results of pesticides in agricultural products collected in each district of Japan have been reported in several papers, but the number of pesticides tested was 200-300 even after implementation of the Positive List System. [11][12][13] In this study, we mainly report the residue results during FY 2005-2009 and compare them with previous data (FY 1995(FY -2004.…”