AOAC OMB Final Action Recommendation (December 2019)-2016.14

2016.14 (Jan. 2019) FOS-03 MLT Report FOR ERP USE ONLY DO NOT DISTRIBUTE

All data received were subjected to statistical analysis as described in the “Appendix D: Guidelines for Collaborative Study Procedures To Validate Characteristics of a Method of Analysis” of the AOAC Official Methods of Analy sis [10] and by using the Excel sheet “AOAC International Interlaboratory Study Workbook, Blind Replicates, Version 2.1” [11]. Outliers were detected using Cochran and Grubbs tests in the workbook. The average concentrations, relative standard deviations of repeatability (RSD r ), relative standard deviations of reproducibility (RSD R ) as well as Horwitz ratio values were estimated from the blind duplicates. Results and Discussion Practice Sample The 14 participating laboratories, randomly coded for identification, started the method evaluation with the analysis of a practice sample. A child formula powder was selected for this purpose, and participants used the sample to set up the method and become familiar with the protocol. Several labs encountered chromatographic problems and some technical support was given. One participant contacted us because they were experiencing sudden lower fructan results for in-house reference materials with a particular batch of the enzyme mixture sucrase, α-amylase, pullulanase and maltase. Further investigations were conducted in the laboratory of the Study Director and at the enzyme supplier. As a result, it was concluded that this particular batch of enzyme was not performing as expected with this assay and should not be used for this MLT. All participants were provided with a new bottle of sucrase mixture of a known satisfactory batch. At that time several labs had already shared their results on the practice sample. They were asked to communicate the batch of the sucrase mixture used for this analysis. The labs that reported results of practice sample with an unsatisfactory batch of sucrase mixture were asked to repeat the analysis with the enzyme batch provided, if this was feasible. Two labs did not repeat this analysis; one lab repeated the analysis with one replicate with MLT samples Day 1 and the second replicate with MLT samples Day 2. A third participant repeated the analysis but with no duplicate and another lab repeated the analysis twice, one duplicate with MLT samples Day 1 and another duplicate determination with MLT samples Day 2. Average results on practice sample analysis can be found in Table 2 . Because of the problems encountered with the sucrase enzyme mixture and other chromatographic problems, the study was delayed by several months for some participating labs. In order to keep the momentum going, it was decided to let all the participants continue with the full set of MLT samples, even if not all practice sample results had been received. Two participants had to drop out because of instrumentation problems and resource availability. The whole set of data from practice sample analysis was split in two parts and statistically evaluated separately. One evaluation was done with all the results obtained with satisfactory batches of sucrase enzyme mixture and another evaluation was done with the results obtained with the unsatisfactory batch. Both evaluations fulfill the Standard Method Performance Requirements (SMPR 2014.002) and can be found in Table 3.