Validation of multiresidue screening methods for the determination of 186 pesticides in 11 agricultural products: broccoli, asparagus, carrot, spinach, burdock, matsutake mushroom, cauliflower, orange, soybean, sesame and millet was done by gas chromatography (GC). The investigated pesticides were selected on the based of such compounds that are commonly used around the world. Although the recovery of 58 of the pesticides was low (< 50%) in some crops, the 128 pesticides that spiked in samples at 0.1 mg/kg showed satisfactory recoveries (≥ 50%) in all crops with relative standard deviation of 4-21%. These validated 128 pesticides were therefore newly acceptable for the pesticide-monitoring programme at the Quarantine Station in Japan; the quantitative limits ranged from 0.005 to 0.1 ppm by GC on a crop basis. The screening methods were applied to monitor the residue from a total of 200 pesticides including 72 previously validated in imported foods at the Station in Japan. Pesticide residue from 188 (12.4%) was found in 1516 samples. Of these, 4 (0.26%) were in violation of Japanese maximum residue limits (MRLs). No detectable residue was found in 1328 (87.6%) samples.

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The applicability of GC, GC/MS and liquid chromatography with tandem mass spectrometry (LC/MS/MS) to screening for 140 pesticides in agricultural products was examined. Validation of multi-residue screening methods for the determination of 88 pesticides in 12 crops (asparagus, cauliflower, burdock, carrot, broccoli, spinach, matsutake mushroom, orange, soybean, sesame, millet and tea) was done by GC and GC/MS. Of the 88 pesticides, 63 were obtained with recoveries in the range from 50 to 150̮ at the 0.1 mg/g level in the 12 crops. Applicability of the o$cial methods in Japan to 74 pesticides, including 22 pesticides with low recovery (̮50̮) by GC or GC/MS analysis, was also examined by LC/MS/MS. LC/MS/MS acquisition parameters were established for 67 pesticides in positive and negative electrospray ionization (ESI) modes. Of 67 pesticides validated in 7 crops using LC/MS/MS at the 0.1 mg/g level, 44 showed recoveries in the range from 50 to 150̮. The occurrence of matrix interference in LC/MS/MS can lead to false-positive detection of MCPA in spinach, cabbage and orange and false-negative detection of four pesticides in orange, spinach, apple and unpolished rice. Good linearity was observed in the studied ranges by GC, GC/MS (r̮0.990) and LC/MS/MS (r̮0.995). Of the total of 140 pesticides validated by GC, GC/MS and LC/MS/MS, 107 were newly recognized as suitable subjects for screening.

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