Whitaker Thomas B, Slate Andrew B, Jacobs Merle, Hurley J Michael, Adams Julie G, Giesbrecht Francis G
Agricultural Research Service, Department of Agriculture, Box 7625, North Carolina State University, Raleigh, NC 27695-7625, USA.
J AOAC Int. 2006 Jul-Aug;89(4):1027-34.
Domestic and international regulatory limits have been established for aflatoxin in almonds and other tree nuts. It is difficult to obtain an accurate and precise estimate of the true aflatoxin concentration in a bulk lot because of the uncertainty associated with the sampling, sample preparation, and analytical steps of the aflatoxin test procedure. To evaluate the performance of aflatoxin sampling plans, the uncertainty associated with sampling lots of shelled almonds for aflatoxin was investigated. Twenty lots of shelled almonds were sampled for aflatoxin contamination. The total variance associated with measuring B1 and total aflatoxins in bulk almond lots was estimated and partitioned into sampling, sample preparation, and analytical variance components. All variances were found to increase with an increase in aflatoxin concentration (both B1 and total). By using regression analysis, mathematical expressions were developed to predict the relationship between each variance component (total, sampling, sample preparation, and analysis variances) and aflatoxin concentration. Variance estimates were the same for B1 and total aflatoxins. The mathematical relationships can be used to estimate each variance for a given sample size, subsample size, and number of analyses other than that measured in the study. When a lot with total aflatoxins at 15 ng/g was tested by using a 10 kg sample, a vertical cutter mixer type of mill, a 100 g subsample, and high-performance liquid chromatography analysis, the sampling, sample preparation, analytical, and total variances (coefficient of variation, CV) were 394.7 (CV, 132.4%), 14.7 (CV, 25.5%), 0.8 (CV, 6.1%), and 410.2 (CV, 135.0%), respectively. The percentages of the total variance associated with sampling, sample preparation, and analytical steps were 96.2, 3.6, and 0.2, respectively.
国内外已针对杏仁及其他坚果中的黄曲霉毒素制定了监管限值。由于黄曲霉毒素检测程序的采样、样品制备和分析步骤存在不确定性，因此很难准确、精确地估计整批货物中黄曲霉毒素的真实浓度。为评估黄曲霉毒素采样计划的性能，对带壳杏仁黄曲霉毒素采样批次的不确定性进行了研究。采集了20批带壳杏仁检测黄曲霉毒素污染情况。估计了与整批杏仁中B1和总黄曲霉毒素测量相关的总方差，并将其划分为采样、样品制备和分析方差分量。发现所有方差均随黄曲霉毒素浓度（B1和总量）的增加而增加。通过回归分析，建立了数学表达式来预测每个方差分量（总方差、采样方差、样品制备方差和分析方差）与黄曲霉毒素浓度之间的关系。B1和总黄曲霉毒素的方差估计值相同。这些数学关系可用于估计给定样本量、子样本量和分析次数（不同于研究中测量的次数）下的每个方差。当使用10千克样本、垂直切割混合机类型的研磨机、100克子样本和高效液相色谱分析对总黄曲霉毒素含量为15纳克/克的批次进行检测时，采样、样品制备、分析和总方差（变异系数，CV）分别为394.7（CV，132.4%）、14.7（CV，25.5%）、0.8（CV，6.1%）和410.2（CV，135.0%）。与采样、样品制备和分析步骤相关的总方差百分比分别为96.2%、3.6%和0.2%。
