Study On Determination Of Choline In Dry Milk By IC And HPLC Methods

Choline is a strong organic alkaline compounds which widespread in the living organisms in the form of free choline, acetylcholine and phospholipid complex. It is an indispensable water-soluble vitamin for growth of animal. Research shows that it plays a very important role in brain growth and the development of cognitive, memory and learning ability. It's another main role to promote liver function. The lack of choline may cause fatty liver, cirrhosis of the liver andarteriosclerosis especially for the elderly, and it can also caused Alzheimer's disease. It is very necessary that adding choline in infant formula and dry milk. Ever country has provision of adding content of choline.The previous methods of detecting choline are perchlorate non-aqueous titration method, Leishi salt colorimetry and Leishi salt weight method. The current national standard GB/T 5413.20-1997 uses the enzyme reaction color spectrophotometer to measure the content of choline. These traditional methods are complex, bad selectivity, having many interfering factors, and they can not identify incorporation of cheap inorganic chloride and amine. In recent years' literatures we can find some new methods such as the high performance liquid chromatography-electrochemical detection method, the chemiluminescence method, the ion chromatography-conductivity detection method etc. But there is not any report about HPLC-ELSD method and HPLC-MSD method to detect the content of choline.This paper establishes ion chromatography (IC), high-performance liquid chromatography-evaporative light scattering detection (HPLC-ELSD) and high-performance liquid chromatography-mass spectrometry (HPLC-MSD) three methods to detect the content of choline in dry milk, and discusses the comparison of these three methods. By orthogonal experiment design L9 (33), fix dry milk quality of 5.00g and hydrochloric acid volume of 30mL, design the concentration of hydrochloric acid (0.5mol/L, 0.8mol/L, 1.0mol/L three levels), the reaction temperature (60℃, 70℃, 80℃three levels), the reaction time (3h, 4h, 5h three levels), and get the best pretreatment condition is 1mol/L HCl at 70℃responsing three hours. Finally, I give the uncertainty evaluation of the determination of choline in dry milk by IC method.The minimum detection limits of three methods of detecting choline are 0.1mg/L, 0.2mg/L and 0.01mg/L. The relative standard deviations are 1.13%, 2.67% and 3.86%. The add recovery are 98.78%～100.72%,96.72%～102.03% and 91.67%～100.02%. The method is simple, high sensitivity, good selectivity while traditional methods can not. This paper adds methods of determination of choline in dry milk, and also gives a reference about determination of choline on other similar products.