Instituto de la Grasa, Consejo Superior de Investigaciones Científicas, 41012 Seville, Spain.
Talanta. 2009 Nov 15;80(1):329-37. doi: 10.1016/j.talanta.2009.06.071. Epub 2009 Jul 7.
In 2008, the first Proficiency Testing Scheme of Chemical Oxygen Demand (1(st)COD-PT(ADG)) was conducted to assess the results obtained for different research groups whose field work is mainly anaerobic digestion. This study was performed using four samples, two solid samples as raw materials and two solid samples to prepare high concentration suspended solid solutions. Invitations were sent to a large number of laboratories, mainly to anaerobic digestion research groups. Finally, thirty labs from sixteen countries agreed to participate, but for different reasons four participants could not send any data. In total, twenty-six results were reported to the COD-PT coordinator. This study showed the importance of continuous participation in proficiency testing (PT) schemes in order to compare the results obtained. Taking into account the lack of a general standard method and high quality certified reference materials (CRMs), the traceability of COD determination is not currently easy to check. In addition, the spread of participants' results obtained was high and pointed to the advisability of using consensus values due to their unreliability. Therefore, the theoretical oxygen demand (ThOD) values were considered as assigned values for all the samples analysed. On the other hand, in this PT the established standard deviation (ESD) has been determined by the Horwitz modified function. Participants of this 1(st)COD-PT(ADG) were asked to give a short report on the analytical method used. Although all the participants used potassium dichromate as their oxidant reagent, their experimental procedures were very different. With the purpose of comparing the results obtained, the different experimental conditions used were classified into five methods, corresponding to two main categories, open and closed reflux. The performance of laboratories was expressed by the z-score, whose value is considered satisfactory when z-score <or=+/-2. The overall analytical data evaluation showed that 64% of z-scores obtained were outside the accepted limits.
2008 年，首次进行了化学需氧量（1(st)COD-PT(ADG））能力验证计划，以评估主要从事厌氧消化工作的不同研究小组的结果。这项研究使用了四个样品，两个固体样品作为原料，两个固体样品制备高浓度悬浮固体溶液。向大量实验室发出了邀请，主要是向厌氧消化研究小组发出邀请。最后，来自 16 个国家的 30 个实验室同意参加，但由于各种原因，有 4 个参与者无法提供任何数据。共有 26 个结果报告给 COD-PT 协调员。这项研究表明，为了比较结果，连续参加能力验证（PT）计划非常重要。考虑到缺乏通用标准方法和高质量的有证参考物质（CRM），COD 测定的可追溯性目前不容易检查。此外，参与者结果的分散度很高，表明由于其不可靠性，使用共识值是明智的。因此，理论需氧量（ThOD）值被认为是所有分析样品的赋值。另一方面，在这项 PT 中，已通过 Horwitz 修正函数确定了建立的标准偏差（ESD）。要求该 1(st)COD-PT(ADG）的参与者简要报告所用的分析方法。尽管所有参与者都使用重铬酸钾作为氧化剂，但他们的实验程序却大不相同。为了比较获得的结果，将使用的不同实验条件分为五种方法，对应于两个主要类别，开放式和封闭式回流。实验室的性能用 z 分数表示，当 z 分数<or=+/-2 时，其值被认为是令人满意的。总体分析数据评估表明，64%的 z 分数超出了可接受的范围。
