a National Food Chain Safety Office , Directorate for Food Safety Risk Assessment , Budapest , Hungary.
J Environ Sci Health B. 2014;49(1):1-14. doi: 10.1080/03601234.2013.836851.
The sampling uncertainty for pesticide residues in carrots, parsley leaves and selected medium size crops was estimated with simple random sampling by applying range statistics. The primary samples taken from treated fields consisted of individual carrots or a handful of parsley leaves. The samples were analysed with QUEChERs extraction method and LCMS/MS detection with practical LOQ of 0.001 mg/kg. The results indicate that the average sampling uncertainties estimated with simple random sampling and range statistics were practically the same. The confidence interval for the estimated sampling uncertainty decreased with the number of replicate samples taken from one lot and the number of lots sampled. The estimated relative ranges of sampling uncertainty are independent from the relative standard deviation of the primary samples. Consequently the conclusions drawn from these experiments are generally applicable. There is no optimum for sample size and number of lots to be tested for estimation of sampling uncertainty. Taking a minimum of 6 replicate samples from at least 8-12 lots is recommended to obtain a relative 95% range of sampling uncertainty within 50%. The cost of sampling/analyses, the consequences of wrong decision should also be taken into account when a sampling plan is prepared.
采用简单随机抽样和范围统计对胡萝卜、欧芹叶和部分中等大小作物中的农药残留进行采样不确定性估计。从处理过的田间采集的初级样本包括单个胡萝卜或一把欧芹叶。采用 QUEChERs 提取方法和 LCMS/MS 检测，实际定量限为 0.001mg/kg。结果表明，简单随机抽样和范围统计估计的平均采样不确定性实际上是相同的。随着从一批中采集的重复样本数量和采样批次数的增加，估计的采样不确定性置信区间减小。估计的相对采样不确定性范围与初级样本的相对标准偏差无关。因此，从这些实验中得出的结论通常是适用的。对于采样不确定性的估计，没有最佳的样本量和测试批次数。建议至少从 8-12 批中采集至少 6 个重复样本，以在 50%内获得相对 95%的采样不确定性范围。在制定采样计划时，还应考虑采样/分析成本以及错误决策的后果。
