Detection of Four Organophosphorus Pesticide Residues in Paddy Rice by Improved QuEChERS-GC-MS/MS

An improved QuEChERS pretreatment method combined with triple quadrupole gas chromatography-mass spectrometry (GC-MS/MS) was established for the detection of four organophosphorus pesticide residues in paddy rice, including dichlorvos, malathion, triazophos and chlorpyrifos. The paddy rice was used as the experimental material, and the samples were processed by using two different pretreatment methods: the conventional QuEChERS pretreatment method (being carried out at room temperature before and after extraction, as well as during purification) and the improved QuEChERS pretreatment method (reducing the temperature of sample solution before and after extraction, as well as during purification). Then, the samples were determined by using the gas chromatography-tandem mass spectrometry (GC-MS/MS) in multiple reaction monitoring (MRM) mode to investigate the linear relationship, limit of quantitation, recovery and precision of the four organophosphorus pesticides. The results showed that the four organophosphorus pesticides in rice had a good linear relationship in the mass concentration range of 0.005−0.5 mg·L⁻¹, with the correlation coefficient (R²) exceeding 0.9999. The detection limits and limits of quantification could meet the standard requirements. When detecting the three pesticide residues including malathion, triazophos and chlorpyrifos at three different spiked levels of 0.02,0.1,0.5 mg·kg⁻¹, there was no significant difference in terms of the detection effect between the traditional QuEChERS pretreatment technique and the improved QuEChERS pretreatment technique. The reproducibility, detection limit and recovery rate of the two methods could meet the standard requirements. However, for the detection of dichlorvos, the improved QuEChERS pretreatment technique showed a recovery rate range of 75.8%−90.4%, which was higher than that of the conventional QuEChERS pretreatment technique (55.8%−62.4%). In summary, the improved QuEChERS pretreatment technique combined with GC-MS/MS operation method had good accuracy and high recovery rate, which was more suitable for the detection of four organophosphorus pesticide residues in paddy rice.