AOAC OMB Final Action Recommendation (December 2019)-2016.14

2016.14 (October 2019) – FOS-03 MANUSCRIPT

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not use post-column addition of sodium hydroxide. This was clearly not ideal but probably not 1 critical when the sodium hydroxide was in sufficient concentration in the eluent, which was the 2 case with the Metrosep Carb 2 column (200 mM NaOH). For the five other participants, 3 concentrations of NaOH in the mobile phase ranged from 6 mM to 25 mM, but below 15-20 mM 4 NaOH the detector has poor response and linear range. Pictures of representative calibration curves 5 of glucose and fructose were requested from those participants and all showed acceptable fit, except 6 one lab. That lab used PA20 with only 6 mM NaOH which gave unusually convex calibration 7 curves. However, as the sugar contents analysed were probably on acceptable portions of the 8 calibration curves, only two results from this lab were identified as outliers by the single Grubbs’ 9 test. Which instrument response (area or height) to use for calibration was not clearly defined in 10 the MLT protocol. One lab used height whereas the other 11 participants used area. A summary of 11 the analytical conditions used by all participating laboratories is presented in Table 8 .

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