顶空色谱法测定土壤中氰和氰化氢残留量

摘要

Cyanogen (C2N2) is a new type of fumigant, a potential replacement of methyl bromide. However, there is still no standard method available at home and abroad for detecting C2N2 and its degradation product, HCN (hydrogen cyanide) in soil. A method for the determination of residues of C2N2 fumigant and HCN in soil using head-space capillary gas chromatography (HS-GC) with a nitrogen-phosphorus detector ( NPD) was developed; and headspace parameters for pretreatment of C2N2 and HCN in the soil was optimized in this study; and quality control parameters such as precision of standard, limit of detection and limit of quantification for the method were validated in experiments. Results showed that incubated in solution of 30% phosphoric acid at 50℃ for 1 h, the sample with C2N2 and HCN concentration in the range of 0. 1 ~ 10 mg kg-1 displayed a linear relationship with correlation coefficients >0. 99 between C2N2 and HCN concentration and chromatographic peak area. The use of this method to determine C2N2 and HCN in soil is subject to a RSD of 4. 58% and 6. 32% (n = 5) , respectively. Of the method, the limit of detection ( LOD) and the limit of quantification (LOQ) of C2N2 and HCN was 0. 016 and 0. 028 mg kg-1 ( S/N = 3) , 0.053 and 0. 093 mg kg-1 (S/N = 10) , respectively. This method was also proved to be convenient in operation, high in sensitivity and least in outside interference, and therefore, applicable to determination of C2N2 and HCN residues in soil.%氰(C2N2)是一种具有替代溴甲烷潜力的新熏蒸剂,建立土壤中C2N2及其降解产物氰化氢(HCN)的标准检测方法具有较重要的意义.本文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C2N2和HCN在土壤中的分析方法,优化了土壤中C2N2和HCN预处理的顶空参数,并通过了方法的精密度、检出限和定量限等质量控制参数的验证实验.结果表明,用30％H2SO4溶液作提取溶剂、顶空平衡温度50C和顶空平衡时间0.5h为最佳的顶空方法参数；在0.1 ～10 mg kg-1的质量浓度范围内,C2N2和HCN的浓度与色谱峰面积线性相关系数均大于0.99.采用该方法测定土壤中C2N2和HCN的相对标准偏差(RSD)分别为4.58％和6.32％(n=5),检出限(LOD)分别为0.016 mg kg-1和0.028 mg kg-1(S/N=3),定量限(LOQ)分别为0.053 mg kg-1和0.093 mg kg-1(S/N=10).该方法操作简单、灵敏度高、干扰少,适用于土壤中C2N2和HCN残留量的检测.