[Determination of seven strobilurin fungicide residues in Chinese herbs by liquid chromatography-tandem mass spectrometry coupled with solid phase extraction].

An LC-MS/MS method was developed for the simultaneously determination of seven strobilurin fungicide residues in Chinese herbs. The strobilurin fungicides include Z-metominostrobin, kresoxim-methyl, dimoxystrobin, picoxystrobin, pyraclostrobin, azoxystrobin and trifloxystrobin. The sample was extracted with ethyl acetate and cleaned-up by an amino SPE column. The seven strobilurin fungicide residues were separated on a C18 column with gradient elution of 1.0 per thousand formic acid and methanol as mobile phases, and detected by ESI-MS in positive ion and selective reaction monitoring (SRM) mode. External standard method was used to the quantification with good linear relationships (r > or = 0. 996). The LOQs were 2 micro g/kg for dimoxystrobin, picoxystrobin and trifloxystrobin, 4 mciro g/kg for pyraclostrobin and azoxystrobin, 10 micro g/kg for Z-metominostrobin and kresoxim-methyl. The recoveries were from 60.4% to 110% with the RSDs between 1.2% and 17%. The developed method is suitable for the determination and confirmation of the seven strobilurin fungicide residues in the three of Eight Zhes ( Ophiopogon japonicus (Thunb.), Scrophularia ningpoensis Hemsl. and Corydalis yanhusuo W T Wang).