4种检出限确定方法的讨论--以离子色谱法测定冬瓜中亚硝酸盐含量为例

Discussion on Four Methods for Determination of Limit of Determination--Based on Ion Chromatography Example of Determining Nitrite in Wax Gourd

目的:目前国内对检测方法检出限的计算没有统一的规定,但在进行检测方法验证或确认时检出限却是必做指标,因此需确定各检出限实验方法的有优缺点,根据实际情况确定最佳的实验方法。方法:本文以离子色谱法测定冬瓜中的亚硝酸盐含量为例,通过4种应用较多的方法,即全程序空白法、加入标准目标分析物法、稀释标准溶液法和计算校准直线的检测能力法获得4个检出限,并加以比较。结果:检出限随确定方法的不同而不同,通过稀释标准溶液获得的检出限因减少了前处理实验步骤的干扰,获得的检出限数值往往较低,更接近于仪器检出限。通过加入标准目标分析物及通过全程序空白获得的检出限更能综合反映实验室检测水平,但受基质限制,若要获得多种物质的检出限,工作量较大。通过校准直线计算检测能力获得的检出限操作简单,但无法全面反映基质、人员、试剂等的综合影响。结论:实验室在进行方法验证或确认时可尝试多种检出限获得方法,对结果进行比较后结合实验室实际情况确定最终的检出限实验方法,同时也建议相关部门在发布检测方法标准时一并列出详细的检出限实验或计算方法,以供比较或借鉴。

Objective:At present,there is no uniform regulation on the calculation of detection limit of detection methods in China,but the detection limit is a necessary indicator when the detection method is verified or confirmed.Therefore,it is necessary to determine the advantages and disadvantages of each detection limit experimental method and determine the best experimental method according to the actual situation.Method:Taking the determination of nitrite content in winter melon by ion chromatography as an example,four detection limits were obtained and compared through four widely used methods,i.e.the whole procedure blank method,the method of adding standard target analyte,the method of diluting standard solution and the method of calculating the detection ability of calibration line.Result:The detection limit varies with the determination method.The detection limit obtained by diluting the standard solution is often lower and closer to the detection limit of the instrument because the interference of the pretreatment experimental steps is reduced.The detection limit obtained by adding the standard target analyte and the blank of the whole procedure can more comprehensively reflect the detection level of the laboratory,but it is limited by the matrix.If the detection limit of a variety of substances is to be obtained,the workload is large.The detection limit obtained by calculating the detection capacity through the calibration line is simple to operate,but it cannot fully reflect the comprehensive impact of the matrix,personnel,reagents,etc.Conclusion:The laboratory can try a variety of methods to obtain the detection limit when verifying or confirming the method.After comparing the results and combining the actual situation of the laboratory,the final detection limit test method is determined.At the same time,it is also suggested that relevant departments publish detailed detection limit experiments or calculation methods when issuing the detection method standards for comparison or reference.