UPLC—MS／MS法测定奶粉中烟酸醮含量

建立一种专属、灵敏、快速的超高效液相色谱串联质谱（UPLC—MS／MS）测定奶粉中烟酸含量的方法。烟酸提取后经强阳离子交换（SCX）固相萃取柱净化，采用BEH—C18超高效液相色谱柱、20mmol／L乙酸水溶液-乙腈（体积比为20：80）流动相分离，以电喷雾离子源正离子方式进行多反应监测（MRM）。试验结果表明，1～500ng／L浓度范围内，烟酸呈良好的线性关系，相关系数R=O．9995。低、中、高3个烟酸浓度添加水平的回收率为78．2％～904％，相对标准偏差小于7％。奶粉中烟酸的检出限为0．25ug／g，定量限为O．75ug／g。采用所建方法对市售6批奶粉进行测定，烟酸含量均符合规定。所建方法适合奶粉中烟酸的含量测定。

Determination of Nicotinic Acid in Milk Powder by Ultra Performance Liquid Chromatography-tandem Mass Spectrometry

A specific, sensitive and rapid method is presented for the determination of nicotinic acid in milk powder by ultra performance liquid chromatography-tandem mass spectrometry （ UPLC-MS/MS ） . Nicotinic acid in the test samples was extracted and cleaned-up with a strong cation exchange （ SCX ） column and analysed by UPLC-MS/MS. Nicotinic acid was separated by a BEH-C18 UPLC column and 20 mmol/L ammonium acetate - acetonitrile （ 20 ： 80, vlv ） as mobile phase, and electrospray ionization was applied and operated in the positive ion mode by MRM. The calibration curves showed good linear relationship in the range of 1 - 500 ng/mL for nicotinic acid with the correlation coefficient of 0.9995. The average recoveries of nicotinic acid in milk powder samples at the three concentrations ranged from 78.2% to 90.4% with the relative standard deviations less than 7%. The limit of detection （ LOD ） and limit of quantification （ LQD ） of nicotinic acid were 0.25 μg/g and 0.75μg/g respectively. Six batches of market milk powder were measured by our method, which showed that the content of nicotinic acid in all tested milk powder meets the specified requirements. The method was proved to be suitable for determination of nicotinic acid in milk powder.