Abstract: The level of trace elements is an important component of safety and quality in milk. While certain elements such as chromium is essential at low level, an excess can result in deleterious effects on human health. This paper described a new method for demonstrating the levels of Fe, K, Ca, Na, Mg, Ag, Al, As, Ba, Be, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se, Tl, V, Zn, Th, U, Hg and Sn in raw cow's milk, using an inductively coupled plasma mass spectrometry(ICP-MS). Using microwave digestion method destroyed the organic matter in milk. Each milk sample was mineralised by using a microwave-assisted digestion procedure. Concentrations of trace elements in digested milk samples were measured by ICP-MS. The selected isotopes were in general the most abundant ones of each element, except in cases where polyatomic or isobaric interferences were detected. Method validation was performed by measuring a GBW 08509 non-fat milk powder and through the use of recovery experiments. Plasma-related matrix effects are also investigated in this paper. The study shows that addition of a set concentration of isopropanol to internal standard solution could eliminate the interference of carbon deposition. The accuracy and reproductibility of the determination of As and Se by ICP-MS was improved by this method.

Key words: milk; trace element; inductively coupled plasma mass spectrometry; microwave-assisted digestion; matrix effects