[Determination of pyriminobac-methyl and bispyribac-sodium residues in rice by liquid chromatography-tandem mass spectrometry based on QuEChERS].

A method was developed for the determination of pyriminobac-methyl and bispyribac-sodium residues in rice by liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with modified QuEChERS. The samples were extracted with acidified acetonitrile, and then purified by octadecylsilane bonded silica (C ₁₈ ) adsorbents. The analytes were separated on a ZORBAX SB C ₁₈ column through a gradient elution using 0.1% (v/v) aqueous formic acid aqueous containing 5 mmol/L ammonium acetate and acetonitrile as mobile phases. Positive electrospray ionization (ESI ⁺ ) was used. Qualitative work was performed using selected dynamic multiple reaction monitoring (dynamic MRM) mode. Quantization was performed using external standard method. The results showed good linearities of pyriminobac-methyl and bispyribac-sodium with correlation coefficients ( r ² ) not less than 0.996. The limits of detection (LODs) of the method were 0.8 μ g/kg for pyriminobac-methyl, and 3 μ g/kg for bispyribac-sodium. The mean spiked recoveries of pyriminobac-methyl and bispyribac-sodium at three spiked levels were 76.6%-85.6% and 73.0%-86.7%, respectively, and the relative standard deviations (RSDs) of pyriminobac-methyl and bispyribac-sodium were 0.9%-3.4% and 1.2%-5.5%, respectively. This method is simple, rapid, sensitive, and suitable for the simultaneous determination of pyriminobac-methyl and bispyribac-sodium in rice.