AOAC SPIFAN ERP & Working Group Method Reviews (July 10, 2019)

At each working standard level, the peak areas or heights of standards injected before and after a set of samples must not increase or decrease by more than 7%. ( c ) Calculation of myo-inositol in samples .—The concentration of myo-inositol in a prepared sample is extrapolated from the standard curve prepared above. From the diluted, prepared sample concentration, the product concentration can be calculated: C p = (C d × D 1 )/S where C p is the concentration of myo-inositol in the product sample in milligrams per kilogram; C d is the concentration of myo-inositol in the prepared sample in milligrams per liter; D 1 is the dilution volume in milliliters; and S is the sample weight in grams. Note : For each set of samples, the control result must be within three standard deviations of the control mean. See Figures 2011.18C and D for typical standard and sample chromatograms, respectively. References: J. AOAC Int . 95 , 937(2012) DOI: 10.5740/jaoacint.CS2011_18 J. AOAC Int. 98 , 1666(2015) DOI: 10.5740/jaoacint.15-107 AOAC SMPR 2011.007 J. AOAC Int . 95 , 295(2012) DOI: 10.5740/jaoac.int.11-0443 * Method adopted by AOAC as an Official Method of Analysis SM and by the International Organization for Standardization as ISO 20637:2015. Posted: February 18, 2016

F. Calculations Before calculating myo-inositol concentrations in samples, compare the myo-inositol standard peaks with the myo-inositol sample peaks and confirm that there are not any interfering compounds and that the myo-inositol sample peak areas or heights are within the range of the myo-inositol standard peak areas or heights. The concentration of myo-inositol cannot be calculated if there are interferences or if the separation is poor. The myo-inositol retention time should be 11 to 13 min depending on the individual analytical column. ( a ) Concentration of working standards . C W = W × 1/0.05 × 1/10 × A 1 /V 1 × A 2 /V 2 = W × 2 × A 1 /V 1 × A 2 /V 2 where C W is the concentration of the working standard solution in milligrams per liter; W is the weight, in milligrams, of myo-inositol standard weighed; 0.05 is the dilution volume of the stock standard in liters; 1/10 is the intermediate standard dilution (10 to 100 mL); A 1 is the aliquot of intermediate standard used, in milliliters; V 1 is the dilution volume of the working standard in milliliters; A 2 is the aliquot of working standard used, in milliliters, if applicable; and V 2 is the dilution volume of the working standard in milliliters, if applicable. ( b ) Preparation of standard curve.— For each working standard concentration, average the peak areas or heights from each two consecutive sets of standards. Prepare a standard curve by performing linear least squares (regression) on the concentrations versus the averaged peak areas or heights. A standard curve must have a correlation of at least 0.999 to be considered acceptable for sample calculations.

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