A long-term, envisioned, objective of the Customs laboratories (CLEN), is the acquisition of harmonization of tasks and laboratory practices and procedures. One such task was the enrichment of the CLEN methods with their performance characteristics (PChs).

The aim of this investigation was to define a valid statistical estimation procedure of the (PChs) (Repeatability and Reproducibility limits) from existing Proficiency Testings’ (PT) data, whose implementation could become the basis for all the other CLEN methods.

The procedure was based on the estimation of the in-between reproducibility, considered to represent the systematic error of all the variations between and within laboratory, promoting thus Harmonization.

There was no rejection of any data and hence, there was no need to follow any statistical rejection rules. The effectiveness and validity of the results was assessed and supported by the conformance to the AOAC minimum analytical requirements and the verification to the comparison with standard methods.

The estimation and evaluation of data for the Butyric Methyl Esters (BAME) and Total fat in biscuits and chocolates, were found to be for BAME at concentration range (1.7–4.0)%m/m, repeatability (r) 0.14 and Reproducibility (R) 0.38 and Total fat at concentration range (10–20)%, repeatability (r) 0.28 and Reproducibility (R) 0.84 and for Total fat at concentration range (20–30)%, repeatability (r) 0.48 and Reproducibility (R) 1.07,though, in the milk products of high protein content, for (BAME) and Total Fat below 1.5%, methods, gave not conforming results. It is suggested that implementation of this estimation procedure will be of great benefit for CLEN laboratories, not only for the method acceptance, but for further investigation in different matrices, aiming to amendments and hence Harmonization. It is proposed that this procedure is reliable and can be implemented to any CLEN method, provided that sufficient PT data are available.

海关实验室（CLEN）的一项长期预期目标是获得任务，实验室操作和程序的统一。其中一项任务是利用其性能特征（PCh）丰富CLEN方法。

这项研究的目的是根据现有能力测试（PT）数据定义（PChs）（重复性和再现性限值）的有效统计估计程序，该程序的实施可能成为所有其他CLEN方法的基础。

该程序基于对中间可重复性的估计，被认为代表了实验室之间和实验室内部所有变异的系统误差，从而促进了协调。

没有任何数据被拒绝，因此，无需遵循任何统计拒绝规则。通过符合AOAC最低分析要求以及与标准方法进行比较的验证，对结果的有效性和有效性进行了评估和支持。

发现对饼干和巧克力中丁酸甲酯（BAME）和总脂肪的数据进行评估和评估，结果表明BAME的浓度范围为（1.7-4.0）％m / m，重复性（r）0.14和重现性（R ）0.38和总脂肪在浓度范围（10–20）％，重复性（r）0.28和再现性（R）0.84，对于总脂肪在浓度范围（20–30）％，重复性（r）0.48和再现性（R）虽然1.07，但在高蛋白质含量的乳制品中，对于（BAME）和总脂肪含量低于1.5％的方法，结果不合格。建议该估计程序的实施对于CLEN实验室将是非常有益的，不仅对于方法的接受，而且对于不同矩阵的进一步研究（旨在修正和协调）也将是有益的。