Method Development and Validation of Quats Group Residues Determination in Vegetables and Fruits by LC-MS/MS Technique

Abstract

        According to the statistics on imported chemicals, herbicides, including chlormequat, diquat, mepiquat, and paraquat, have been used as weed control agents. Diquat and paraquat are the herbicides, while chlormequat and mepiquat are synthetic substances for controlling plant growth. The inappropriate use of these agents, especially paraquat, can lead to environmental contamination and cause adverse effects on consumers' health. WHO has categorized paraquat’s toxicity as class II, which is moderately hazardous; moreover, paraquat is also classified as a category 4 hazardous substance according to the Hazardous Substances Act, B.E. 2563 (2020). This research aimed to develop and validate the analysis method for the four “quat” substances in fruits and vegetables. Firstly, the sample extraction was undertaken by using acidified methanol, and then centrifuged. After that, the extraction solution was examined to identify and quantify the herbicide residues by LC-MS/MS. The results indicated that the LOD and LOQ were 0.005 and 0.010 mg/kg, respectively, and the linearity was shown in the range of 0.01–0.20 mg/kg. The accuracy of this method was approximately 66.2–117.2%, and the precision was between 0.4% and 14.5%. This method has been recognized as ISO/IEC 17025:2017 accredited method since 2020. Therefore, it is suitable to be applied in a laboratory for consumer protection and law enforcement purposes. This method was also used to survey the contamination of these substances in 219 fresh vegetables and fruits in 2020. It was found that three samples contained herbicide residues: mepiquat in two samples and chlormequat in the other one, while paraquat residues were not detected in any of the three samples.