Elements analysis of infant milk formula by ICP-OES: a comparison of pretreatment methods

Sample pretreatments are critical steps for achieving true and precise results in element analysis for infant milk formula. In this study, we made a comparative study of four pretreatment methods: dry ashing (DA), wet ashing (WA), microwave ashing (MA) and slurry dispersion analysis. Nine elements (Ca, Cu, Fe, K, Mg, Mn, Na, P and Zn) were determined by inductively coupled plasma optical emission spectrometry. Infant formula (GBW08509) with certified values was used for assessment of trueness and precision. The data showed that all relative standard deviations (RSD) of the observed values were <15 %. In contrast to other pretreatment, results for MA had the lowest RSD (≤5 %) for all the elements. For Cu and Mn, there was no significant difference between measurement results and certified values in four pretreatments. But, after DA and WA the results for Ca, K, Na, P and Zn differed significantly from the certified values.