| Vitamin D, Choline and L-carnitine are indispensable vitamins for growth of animal. They play a very important role in brain growth and the development of cognitive, memory and learning ability. It is very necessary to add Vitamin D, Choline and L-carnitine in infant formula and dry milk for the lack of Vitamin D, Choline and L-carnitine may cause many diseases.Previous methods for the detection of Vitamin D, Choline and L-carnitine included high performance liquid chromatography (HPLC) and spectrophotometry methods. The current Chinese national standard, GB/T 5413.20-1997, uses the enzyme reaction color spectrophotometer to measure the content of choline. In accordance with GB/T 5413.9-1997, high performance liquid chromatography (HPLC) is adopted to detect vitamin D. As yet, there is no Chinese national standard method to detect L-carnitine. As the content of Vitamin D and L-carnitine is very low and the disturbance in milk powder is very great, it is difficult to accurate quantification using HPLC method, and the spectrophotometry method for the determination of choline have difficult in acquiring accurate results.Some new methods, such as the high performance liquid chromatography- electrochemical detection method, the chemiluminescence method and the ion chromatography-conductivity detection method can be found to determinate the content of choline, and precolumn derivatization HPLC method to measure the L-carnitine etc can be found in recent years' literatures. But till now there is no any report about the detection of vitamin D, choline and L-carnitine using high performance liquid chromatography - mass spectrometry (HPLC-MS) method. This method can avoid the complex matrix disturbance in milk powder sample and the determination limit was 10μg/L,0.1μg/L and 1.0μg/L, respectively. The method was proved to be simple and accurate, and can been applied to the determination of vitamin D, choline and L-carnitine in milk powder sample with satisfactory results.
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