Determination of myo-inositol in infant formulae and milk powders using capillary gas chromatography with flame ionisation detection

A gas chromatographye-flame ionisation detection method was developed to establish the content of myo-inositol in milk powders and infant formulations subsequent to formation of the volatile trialkylsilyl derivative. Samples were prepared by acid digestion, thereby releasing inositol from its multiple bound forms. A digestion time of 4 h at 114 degrees C was sufficient to hydrolyse potentially interfering carbohydrates and quantitatively recover bound inositol from milk-based products. Single laboratory method validation showed a within-day relative standard deviation (RSDr) of 5.9% and between-day relative standard deviation (RSDiR) of 9.6%. A between-laboratory (n - 7) collaborative study yielded an average reproducibility (RSDR) of 12.8%, considered fit-for-purpose as a quality control method for milk-based infant formulations. Soy-based products, containing significant inositol hexaphosphate (IP6, phytic acid), required 32 h for release of all inositol. Although current regulations do not specify the inclusion of IP6 in an inositol measurement, the current method allows for its discrimination if present. (C) 2014 Elsevier Ltd. All rights reserved.