Chloride in Milk, Milk Powder, Whey Powder, Infant Formula, and Adult Nutritionals Potentiometric Titration: Collaborative Study, Final Action 2016.03
Abstract Background: In September 2015, both AOAC Official Methods 2015.07and 2015.08 single-laboratory validations (SLVs) were reviewed against Standard Method Performance Requirements® (SMPR) 2014.015by the AOAC Stakeholder Panel for Infant Formula andAdult Nutritional (SPIFAN) Expert Review Panel (ERP). Looking at the similarity and uniqueness of the two methods, the authors agreed, as advised by the ERP, to work together to merge the two methods intoone. This combined method was assigned Method 2016.03. Objective: In order to determine the repeatability and reproducibility of the AOAC First Action 2016.03 method, a collaborative study was organized. The study was divided in two parts: (Part 1) method set up and qualification of participants and (Part 2) collaborative study participation. During Part 1, each laboratory was asked to analyze two practice samples. The laboratories that provided results within a range of expected levels were qualified for Part 2, during which they analyzed 25 samples in blind duplicates. Results: The results were compared with SMPR 2014.015 established for chloride. The precision results (repeatability and reproducibility) were within therequirements stated in the SMPR. In general, the precision results (repeatability and reproducibility)were well within the limits stated in the SMPR. Repeatability ranged from 0.4 to 1.9%, in accordance with data obtained during SLV, with reported RSD of repeatability from 0.03 to 1.6%. Meanwhile, reproducibility ranged from 0.6 to 4.0%. Finally, the Horwitz ratio values were all below 1, from 0.2 to 0.9%. Conclusions: The ERP determined that the data presented met the SMPR and accordingly recommended the method to be granted Final Actionstatus. In January 2018, the Official Methods Boardapproved the method as Final Action.