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

A gas chromatography–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 °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.