Multi-elemental fractionation in milk whey by size exclusion chromatography coupled on line to ICP-MS

A fast hybrid technique based on HPLC coupled to ICP-MS was used to study elemental fractionation patterns in milk whey of different types of milk ( human, cow and formula milk) taking advantage of the multi-elemental capability of ICP-MS. Milk whey was obtained from the corresponding whole milk samples by resorting to ultra-centrifugation. The method described separated the different fractions in a high-pressure column, based on size exclusion chromatography (SEC) on a TSK G 2000 SWXL column, coupled on-line to the inductively coupled plasma mass spectrometer for multi-elemental detection. After optimisation of the instrumental conditions, the method was applied to investigate the fractionation pattern of Fe, Cu, Zn, Mn, Sr, I, Br, Ca and Mg in four different samples of each kind of milk whey under study ( human, raw cow, UHT cow and formula milk whey). As a result of this, it was found that the elemental binding patterns in human milk were different from those observed in cow and formula milks. This finding seems to indicate the presence in human milk of specific ligands. Thus, bioavailability of essential elements seems to be different in man. Therefore, more care and further study should be given to the characteristics of cow and formula milks used for human nutrition, particularly in babies and infants.