水稻中嘧草醚顺反异构体的检测及储藏稳定性

Determination of pyriminobac-methyl isomers in paddy and its storage stability

目的采用超高效液相色谱-串联质谱法(ultra performance liquid chromatography-tandem mass spectrometric,UPLC-MS/MS)检测水稻(糙米、谷壳、秸秆)样品中嘧草醚顺反异构体(E)-嘧草醚和(Z)-嘧草醚的残留量,考察嘧草醚顺反异构体在水稻中的储藏稳定性。方法样品经乙腈提取,N-丙基乙二胺(primary secondary amine,PSA)净化,上清液过膜后采用UPLC-MS/MS进行测定,外标法定量。结果本方法在0.0001~0.0500 mg/L范围内线性响应良好(r2≥0.9995)。在0.010、0.10和1.0 mg/kg添加水平下,(E)-嘧草醚和(Z)-嘧草醚的平均回收率分别为95.1%~109%和96.4%~110%,相对标准偏差均小于7.12%(n=5),方法检出限为0.01 Hg/kg。糙米、谷壳和水稻秸秆样品在-18℃储藏条件下,(E)-嘧草醚和(Z)-嘧草醚的平均降解率均小于30%。结论本方法具有准确和灵敏的特点,能满足水稻中嘧草醚顺反异构体残留量的定量分析要求。-18℃条件下,(E)-嘧草醚和(Z)-嘧草醚在水稻(糙米、谷壳、秸秆)样品中的储藏稳定期至少为182 d。

Objective To determine the residues of pyriminobac-methyl isomers(E)-azoxystrobin and(Z)-azoxystrobin in paddy(brown rice, husk and straw) by ultra performance liquid chromatography tandem mass spectrometry(UPLC-MS/MS), and investigate the storage stability of the pyriminobac-methyl isomers in paddy. Methods The samples were extracted with acetate, and then purified with primary secondary amine(PSA) sorbent, finally detected by UPLC-MS/MS after filtering the supernatant. The samples were quantified by external standard method. Results This method had a good linear response in the range of 0.0001-0.0500 mg/L with correlation coefficients r^2 no less than 0.9995. The average recoveries of(E)-pyriminobac-methyland(Z)-pyriminobac-methyl at 3 spiked levels(0.010, 0.1 and 1.0 mg/kg) were 95.1%-109% and 96.4%-110%, respectively. The relative standard deviations(RSDs) were less than 7.12%(n=5), and the limits of detection(LOD) was 0.01 μg/kg. The average degradation rates of(E)-azoxystrobin and(Z)-azoxystrobin were less than 30% for crude rice, chaff and rice straw samples stored at -18℃. Conclusion This method is accurate and sensitive, and can meet the requirements of quantitative analysis of pyriminobac-methyl isomersresidues in paddy. At -18℃, the storage stability period of(E)-azoxystrobin and(Z)-azoxystrobin in paddy(brown rice, husk, straw) samples is at least 182 d.