顶空气相色谱法测定小麦中熏蒸剂氰及其代谢物氰化氢的残留量

采用溶剂顶空毛细管气相色谱-氮磷检测器(NPD)建立了熏蒸剂氰(C2N2)及其代谢物氰化氢(HCN)在小麦中残留的分析方法。在气相与液相体积比(β)为4时,采用GS-Q大孔毛细管色谱柱和进样60 μL顶空气体,可提高C2N2和HCN的分离效果和灵敏度。以质量分数为50%的磷酸作溶剂,在25 ℃下平衡4 h,C2N2和HCN在液相与气相间的分配系数(k)分别为0.44和48.82。平衡温度和基质对C2N2和HCN挥发的影响存在差异,而盐化效应的影响较小。用50% 的磷酸提取熏蒸过的小麦72 h,释放至顶空的C2N2和HCN的量最大,用添加标准品的小麦作标准可评价熏蒸小麦中C2N2和HCN的残留量。C2N2和HCN标准曲线的线性范围分别在质量浓度为1.0~500 μg/L和1.2~500 μg/L之间,相关系数(R2)分别为0.999 7和0.999 8,相对标准偏差分别为4.6%和7.4%,检出限(LOD)分别为0.032和0.145 mg/kg,定量限(LOQ)分别为0.107和0.483 mg/kg。方法操作简单、灵敏度高、干扰少,适用于小麦中C2N2和HCN残留量的检测。

Determination of fumigant residues of cyanogen and its metabolite hydrogen cyanide in wheat by headspace gas chromatography

A method for the determination of fumigant residues of cyanogen(C2N2) and hydrogen cyanide(HCN) in wheat using headspace(HS) capillary gas chromatography(HS-GC) with nitrogen- phosphorus detection(NPD) was developed.The separation efficiency and sensitivity for C2N2 and HCN were improved by using a GS-Q megabore capillary column and by injection of 60 μL of HS gas with a splitting ratio of 4.Optimum HS conditions were found to be incubation at 25 ℃ for 4 hours in the presence of 50% phosphoric acid as an acidifying reagent.The distribution coefficient (k) was 0.44 and 48.82 for C2N2 and HCN,respectively.C2N2 showed a different vaporization behaviour to HCN with respect to temperature and matrix effect.The salting-out effect was relatively small for C2N2 and HCN.Optimum release into the headspace of C2N2 and HCN in aged wheat after solvent extraction with 50% phosphoric acid for 72 hour were obtained.C2N2 and HCN residues in aged wheat were estimated by using fortified wheat as standards.The calibration graph was linear over 1.2-500 μg/L of C2N2 and 1.0-500 μg/L of HCN with correlation coefficients(R2) of 0.999 7 and 0.999 8,respectively.The limits of detection(LOD) of C2N2 and HCN were 0.032 mg/kg(RSD 4.6%) and 0.145 mg/kg(RSD 7.4%),the limits of quantitation(LOQ) of C2N2 and HCN were 0.107 mg/kg and 0.483 mg/kg,respectively.This method was also proved to be convenient in operation,high in sensitivity and effective in purificatio,and applicable for determination of C2N2 and HCN residues in aged wheat.