Optimization And Application Of LC-MS-MS Detection Method For Neonicotinoid Insecticides

Rapid detection of residues of multiple neonicotinoid pesticides is of great importance to ensure the safety of agricultural products. There are variety of instruments and techniques used to detect a single neonicotinoid pesticide, but the detection method for residues of multi-pesticides is still lacking. LC-MS instrumentation provides an important foundation for the establishment of a multi-residue detection method for neonicotinoid pesticides. In this paper, focusing on the material for strawberry fruit samples, a practical multi-residue detection method for neonicotinoid pesticides was established. The main results were summarized as follows:1. Optimization of measuring conditions of chromatography and mass spectrometry for 8 selected neonictinoid insecticides. By selection and comparison a optimized conditions for LC-MS-MS detection method were determined as:C18 capillary column; acetonitrile-water (0.1%formic acid) as the mobile phase for gradient elution; the flow rate was 0.7mL/min; ESI+ion sources was used for multiple reaction monitoring (MRM); qualitative and quantitative ions of 8 pesticides were listed in Table 2-1. With this optimized conditions,8 neonictinoid insecticides were well separated, qualified and quantified. The linear detecting range was 0.01-1mg/L, with a correlation coefficient> 0.99. The lowest detection limits for all 9 pesticides were all 0.01mg/kg.2. Establishment of the sample pretreatment techniques for the strawberry fruits. The sample was extracted by vibration in 50 mL acetonitrile for 1 hour, then was purified by NH2 SPE column and eluted by mixture of acetone and dichloromethane (V:V,20:80); the elution solvent was evaporated by nitrogen and diluted to certain volume by mobile phase solvent, and was ready for detection by LC-MS-MS system. With this pretreatment, the recoveries were 81.1-103.7% for 8 neonictinoid insecticides and RSDs were<10%for samples containing the insecticide at the content of 0.01,0.05, and 0.1 mg/kg (n= 5).3. Detection of the neonicotinoid pesticide residues in strawberries samples. By using the above optimized LC-MS-MS detection method and the sample pretreatment technique, neonictinoid insecticides residues were measured in 54 strawberry samples collected from 6 production bases in Jiangsu province. The results showed that the detection rate of Acetamiprid was 55.56%, respectively, but the residue contents in the strawberry was lower than the national standard. Further dietary intake risk assessment of acetamiprid showed that all the strawberry were safe for eating.In summary, this study established a multi-residue detection method for neonicotinoid pesticides, and the pretreatment technique for strawberries samples. These methods are valuable in the pesticide residues detection and safety assessment of the agricultural products.