正态分布检验在地下水检测质量控制中的应用

对地下水调查中37种必测组分检测过程的替代物进行筛选,应用D’Agostino法对替代物的测量结果进行正态性检验。利用正态分布函数"3σ"原则,定义了各替代物质量控制指标的有效区间。应用正态函数随机变量的数学期望和方差,计算得到各替代物有效区间内的正态函数分布概率均大于97%,替代物过程能力指数计算结果表明,二溴氟代甲烷、甲苯-d8、对溴氟苯、1,2-二氯苯-d4、氟苯等挥发性有机污染物分析过程选用的替代物质量控制过程处于稳定的监控状态;2,4,5,6-四氯间二甲苯、二丁基氯菌酸酯、p-三联苯、十氯联苯等半挥发性有机污染物分析过程选用的替代物监控指标分析过程能力不足。建议参考美国EPA方法中有关监控指标质量控制区间的要求,适当放宽对半挥发性有机物检测流程中选用的替代物质量控制区间的有效范围。正态分布在地下水检测过程质量控制中的应用,为实验室检测过程的质量管理提供了科学、有效的数学依据。

Application of Normal Distribution Test in Quality Control for Analytical Data of Groundwater Samples

The surrogates for the determination of 37 organic compounds in groundwater samples have been screened out and D’Agostino method has been applied to the normal distribution test for the determination results.Based on the "3σ-principle" of normal distribution theory,the effective ranges of the quality control indexes for each surrogate were fixed.And calculating using mathematical expectation and variance for the random variable of normal distribution functions,the normal distribution probability for analytical data of all surrogates is greater than 97% within effective ranges.The calculated process capability indexes of the surrogates for the volatile organic compounds (VOCs) of dibromofluoromethane,toluene-d8,4-bromofluorobenzene,1,2-dichlorobenzene-d4,fluorobenzene were between 1.00 and 1.33,indicating the effective monitoring for the analytical process.However,the process capability indexes of the surrogates for the semi-VOCs of 2,4,5,6-tetrachloro-m-xylene,dibutyl chlorendate,p-Terphenyl,decachlorobiphenyl were between 0.67 and 1.00,indicating lack capacity for monitoring the analytical process.Consulting the related regulations of EPA method,authors suggested that the quality control criteria for surrogates of 12 semi-VOCs in groundwater analysis should be handled flexibly.The quality control method has been successfully applied to the analysis of organic compounds in groundwater.