Simultaneous determination of five pesticides residues in Anoectochilus roxburghii by HPLC-MS/MS method

Objective： To establish a HPLC-MS/MS method for simultaneous determination of five pesticides residues including tebuconazole，metalaxyl-M，thiophanate-methyl，oxytetracycline and abamectin in Anoectochilus roxburghii.Methods： The samples were extracted by acetonitrile solution and purified by QuEChERS method.Separation was performed on Agilent Eclipse Plus C18 column（50 mm×2.1 mm，1.8 μm） with the mobile phase consisting of 0.1% formic acid（A） and acetonitrile（B） by gradient elution（0-1.0 min，90% A；1.0-3.0 min，90%-70% A;3.0-5.0 min，70%-30% A;5.0-8.0 min，30%-10% A;8.0-14.0 min，10% A;14.0-15.0 min，10%-90% A;15.0-17.0 min，90% A）.Detection was performed on a triple quadrupole tandem mass spectrometry with electrospray ionization source operating in positive ion mode under multiple reaction monitoring（MRM） mode.Results： The calibration curves of five pesticides showed good linearity coefficients（r>0.99）.The average recoveries ranged from 72.7% to 94.9%（n=6），and the relative standard derivations（RSDs） were within 1.8%-10.3%（n=6）.The detection limits of tebuconazole，metalaxyl-M，thiophanate-methyl，oxytetracycline and abamectin were 0.6，0.2，0.3，0.2，5.0 μg/kg，and the quantitation limits of 5 pesticides were 2.0，0.5，1.0，0.6 and 10.0 μg/kg respectively.Conclusion： The established method was proved to be sensitive，simple and reliable，and could be applied for the determination of these five pesticides in Anoectochilus roxburghii and quality control in the planting process.