Fast determination of myo-inositol in milk powder by ultra high performance liquid chromatography coupled to tandem mass spectrometry

A simple and fast method has been developed and validated for the determination of myo  -inositol in milk powder samples, using solid–liquid extraction with water (0.01% formic acid, v/v):methanol (1:1, v/v). The determination was carried out by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC−MS/MS) using an electrospray ionisation source (ESI) in positive mode. Chromatographic separation was carried out using as mobile phase water (0.01% formic acid, v/v) and methanol in gradient mode. Data acquisition under MS/MS was achieved by applying selected reaction monitoring, using 181.0→$\to$109.0 and 181.0→$\to$81.0 for quantification and confirmation purposes, respectively. The technique provides a sensitive and selective determination of myo-inositol in the analysed samples, with a run time of 4 min. The limit of detection and quantification were 0.2 and 0.5 mg kg⁻¹, respectively. The method was applied to six fortified commercial milk powder samples containing myo-inositol amounts ranging from 290 to 2200 mg kg⁻¹.