Study on establishment of residual analysis methods and residue degradation regulation of natural pyrethrin in barley plants and soil on Qinghai Plateau

A sensitive and selective method was developed for the determination of pyrethrin residues in highland barley (kernel, stem and root) and soil in Qinghai Plateau by gas chromatography (LC-MS/MS). Multi-residue analysis of pyrethrin in samples involves simple extraction with acetonitrile, salt-out with Nacl, MgSO4 absorption of water, cleaning with GCB and PSA, respectively, followed by separation with XR-ODS II column, and multi-reaction detection mode detection using a positive mode electrospray ionization source (ESI+). The results showed that the 6 different components of pyrethrin had good detection effect in the concentration range of 0.01∼1.0 mg/L, and the correlation coefficient was greater than 0.9990. The limits of quantitation of each component on each substrate were 0.01∼0.05 mg/k, the average daily recoveries were 87.58∼95.44%, the relative standard deviations were 0.4∼3.8%. The half-life of pyrethrin in barley grains, stems and soil was 0.77∼2.57 d. In soil and highland barley, the maximum dose of pyrethrin and twice the maximum dose of pyrethrin were applied, and the final residue of 7 days after treatment was less than 0.2mg/kg. The degradation behavior of pyrethrin in soil at three test sites showed that organic carbon and pH were important factors affecting the degradation of pyrethrin, and the effect of pH on the degradation of six pyrethrin components was greater than that of organic carbon. These studies provide theoretical basis for environmental safety evaluation caused by pyrethrin use in Qinghai Plateau.