AOAC SPIFAN WPC ERP-Final Action Review (Nov. 2017)

2016.15 (Nov. 2017) - WPC-31 MLT-Final Action Review

FOR ERP USE ONLY DO NOT DISTRIBUTE

Statistical evaluation was carried out using the AOAC template and results are summarized in Table 2016.15H. A few outliers were detected using Cochran or Grubbs tests (see Table 2016.15H for details) and deletion of the corresponding values did not result in supplementary outliers (i.e. rejection rate would be 10.5% at most for Formula 3). It was decided to keep all values for the statistical analysis presented in Table 2016.15G because no obvious explanation could be found to justify removal of the outliers. Statistical values calculated before and after outlier removal are presented in Table 2016.15I for information. Except for the NIST SRM 1849a sample (SPIFAN 4, codes KGSZ273 and LTCT316), relative repeatability (RSD r ) values ranged from 0.83 to 2.11%, relative reproducibility (RSD R ) values ranged from 2.18 to 4.22%, and HorRat values ranged from 1.02 to 1.85, all meeting the requirements of SMPR 2012.002 [4] and the AOAC multi-lab testing guideline [6] for all sample pairs (all samples are commercial formulas). In all those samples, the measured value fell between 98 and 108% of the declared value (For Formula 2 and Formula 6, the declared value was “>60%” and the measured value was around 63.5%). There is no clear explanation for the atypically high recovery of whey in the NIST SRM 1849a sample. The reference value was calculated from the formulation and is an estimation of the whey content, not a reference or certified value. In this study, 12 labs used instruments and capillaries from Beckman/Sciex. Labs 5 and 6 used instruments from Beckman but the capillaries were made by a Chinese manufacturer. Labs 15 and 16 used an instrument from DeltaDOT, labs 17 and 18 used an instrument from Agilent, and lab 19 used the CL1020 instrument from the Chinese manufacturer Huayanglimin. Labs 15 used the capillaries made by a Chinese manufacturer; lab 16 used the capillary purchased in UK; lab 17 and 18 used capillaries from the same brand as their instrument, lab 19 used Beckman/Sciex capillaries. Even though the migration times of the proteins were delayed compared to the Beckman instrument, the final results were not significantly different. This indicates that the method can be performed using a wide variety of instruments and capillaries. Feedback from the participants Participants were asked to document any deviations from the method and any pertinent comments and observations based on their experience in adapting the method into their laboratory. In general, comments were positive with respect to the ease of use of the method.

Sample treatment

The buffer blank in the sample sequence run can be used to indicate possible contaminations in reagents or centrifuge tubes. A peak appearing after the 10 kDa