No abstract

Milk is the main basic foods for infants, because they contain essential nutrients (proteins, lipids, carbohydrates) and micronutrients (minerals, vitamins, enzymes) 1. The ratio of calcium to phosphorus (Ca/P ratio) in milk and dairy products is an important factor for the absorption of calcium. The absorption of calcium deteriorate when the Ca/P ratio is too low in the diet 2. According to the official standards (CODEX STAN 72-1981) of FAO/WHO, the ratio of Ca/P in infant formula should be in the range 1-2 3. Inductively coupled plasma mass spectrometry (ICP-MS), one of the most sensitive techniques, has been used extensively for determining trace elements in a wide range of foodstuffs 4-8. Unfortunately, the determination of Ca or P by ICP-MS suffers from high background problems: 40 Ca + (96.97 %) is interfered by 40 Ar + , 44 Ca + (2.06 %) is interfered by 12 C 16 O2 + and 14 N2 16 O + , 42 Ca + (0.64 %) is interfered by 40 ArH2 + and 31 P + (100 %) is interfered by 14 N 16 OH + , 15 N 16 O + and 14 N 17 O + 9,10. Some authors used the cool or cold plasma technique to alleviate the Arbased interferences in ICP-MS analysis 11,12. However, it cannot eliminate the interfering N-oxide or hydroxides ions on P determination 13. Recently, it has been proved that the dynamic reaction cell (DRC) technique coupling with ICP-MS can alleviate effectively mass spectral interferences 14-17. Chen et al.