采用酶抑制法检测大蒜中农药残留的改进方法

An Improved Enzyme Inhibition Method for Detection of Peptide Residues in Garlic

针对采用酶抑制法检测大蒜中有机磷和氨基甲酸酯类农药残留存在假阳性的问题,提出一种改进检测方法。将待测样品的酸碱度调节至最佳pH值后再进行检测,该方法不仅有效地减小了大蒜检测中产生的含硫物质对乙酰胆碱酯酶的抑制作用,同时保证了有机磷和氨基甲酸酯类农药的正常检测。对空白大蒜样品、农药水溶液样品分别进行不同pH值条件下的检测实验,结果发现:在一定范围内调节待测液的酸碱度没有影响农药的定性判别结果,但却极大地抑制了大蒜样品假阳性的发生,因此将该pH值范围(约pH8.0～9.0)确定为最佳检测条件。进一步在pH9.0条件下对分别添加8种农药(甲胺磷、敌百虫、乐果、克百威、辛硫磷、毒死蜱、敌敌畏、甲萘威)的大蒜样品进行检测,与pH7.5农药缓冲液的判定结果符合度达到91.7%。因此,该方法通过改进检测条件——pH值,实现了大蒜中农药的酶抑制法检测。且该方法简单、低成本、有效,适用于现场快速检测的场合,同时可推广到其他含硫蔬菜的检测。

An improved method was proposed to rectify false positive （FP） results from the determination of organophosphorus and carbamate pesticides in garlic by enzyme inhibition method. Sample solutions were adjusted to the optimum pH prior to detection, considerably reducing the inhibition effect of formed sulfides on acetylcholinesterase （ACHE） while allowing the determination of organophosphorus and carbamate pesticides. The results obtained for the determination of blank garlic and pesticide solutions under different pH conditions indicated that pH adjustment in the optimum range of about pH 8.0 to 9.0 of sample solutions was very effective for avoiding FP results without affecting qualitative identification of organophosphorus and carbamate pesticides. For garlic samples spiked with varying conditions of 8 pesticides （methamidophos, trichlorphon dimethoate, carbofuran, phoxim, chlorpyrifos, dichlorvos and carbary）, the results obtained at pH 9.0 showed a 91.7% consistency with those observed at pH 7.5. In conclusion, the improved pretreatment method presented by adjusting pH in this study is simple, low-cost and effective and applicable for in situ rapid detection and can also be expanded to other sulfur-containing vegetables.