AOAC OMB Final Action Recommendation (December 2019)-2016.14

2016.14 (October 2019) – FOS-03 MANUSCRIPT

FOR ERP USE ONLY DO NOT DISTRIBUTE

Method adaptations by MLT participants 1 The participants were asked to communicate any deviations from the MLT protocol and the 2 reported digressions were numerous. Regarding the sample reconstitutions, one lab downsized the 3 reconstitution rate to 15.0 g product + 120.0 g water because containers of appropriate dimensions 4 were not available, but the ratios were preserved. Another participant applied a different 5 reconstitution protocol by weighing 12.5 g of powder and adding 100 mL of water (using a 6 volumetric flask) or weighing 10 g of powder and adding 90 mL of water (using a measuring 7 cylinder) for SRM 1869. 8 Several participants did not understand the importance of the precision of the reconstitution rates 9 and applied inconsistent ratios of powder/water. To remedy this, which would lead to artificially 10 elevated precision data, reconstitution weights were requested from all participating labs and the 11 final fructan results corrected accordingly. In one laboratory, the solution “A” was diluted by 12 weight instead of by volume. 13 Regarding optional Carrez clarification, four labs used it and seven labs did not. One participant 14 performed both procedures (with and without Carrez clarification), but only the data without 15 clarification were used for data analysis as one sample result was missing for the procedure with 16 Carrez clarification (results with and without Carrez treatment were comparable). Several labs 17 mentioned they had to use slight positive pressure or pump assist in order to help elution from the 18 SPE columns. A remark describing this procedure has been added in the final method. 19 Regarding chromatography, the participants introduced many deviations. Only three labs did 20 not deviate from the chromatographic conditions described in the protocol. Eight participants used 21 a PA1 column, two labs used a PA20, one lab used a PA10 and one lab used a Metrosep Carb 2 22 column. Some labs (4) used a 4 mm PA1 column instead of the 2 mm mentioned in the protocol 23 and they adapted the main and post-column flow rates accordingly. Several participants also 24 adapted the chromatographic conditions according to their equipment and habits (elution program, 25 injection volume, oven temperature, etc.). Besides all these modifications, six participating labs did 26

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