OMB Meeting Book_9-11-14

16 - Overall conclusions of MLT on fatty acids

 The majority of results provided for individuals and groups of fatty acids in all samples ( i.e. dairy, infant formula and adult nutritional products) were in agreement with expectations ( i.e. results gained over the years, proficiency tests, SLV) and limits fixed in SMPR.  Results provided for some fatty acids (who can contribute also to sums) were significantly influenced by chromatography or analyst ( i.e. response factors of instrument, co-elution, wrong peak identification or integration but also error in the reporting).  The instruction to identify and report some fatty acids ( i.e. TFA) were not carefully applied by some participants and the real method capability for TFA is impacted. TFA results were seen above the limits fixed in SMPR.  The removal of outliers in ISO-5725 is based principally on Cochran & Grubbs and considerations given above ( i.e. instructions given not followed) were not taken into account in the current statistical evaluation. The labs affected by the problem can be also identified by Mandel’s H & K.  Once again for this kind of method the chromatography performances is a key parameter, the results obtained for the majority of labs showed that optimal performances can be achieve with some efforts.

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