正交试验结合液质法测定乳粉中左旋肉碱

Determination of L-Carnitine in Milk Powder by HPLC-MS/MS Combined with Orthogonal Experiment

建立了乳粉中左旋肉碱含量的液相色谱串联质谱测定法。样品经20%甲酸水-乙腈（7︰3,V/V）提取,正交试验优化皂化条件,为15%氢氧化钾溶液,按5︰1（提取液︰氢氧化钾）在60℃,皂化20 min。以5 mmol/L乙酸铵（含0.1%甲酸）-乙腈为流动相,采用CAPCELL PAK CR色谱柱（150 mm×2.0 m（I.d）,5μm）进行分离。采用多离子反应监测（MRM）方式,正离子模式电喷雾质谱进行检测,定量定性离子对分别为（m/z）162.2/103.2,162.2/85.1。在优化条件下,样品在5 min之内完成分析。在200-2 000 ng/m L范围内线性良好（R=0.999 8）。左旋肉碱的检出限为97.5μg/kg,定量限为0.33 mg/kg。低、中和高3个水平的加标回收率平均在97.5%-102.5%之间,RSD值为2.4%-3.2%。方法快速简便,灵敏度高,重复性好,已应用于乳粉中左旋肉碱的测定。

A high performance liquid chromatography-tandem mass spectrometry （HPLC-MS/MS） method was developed for the determination of L-camitine in mill powder. The conditions of extraction, saponification and parameters of LC-MS were optimized. After extraction with 20% formic acid-acetonitrile （7 ： 3, 11/11） and saponification with 15% KOH, 5 ： 1, 60 ℃, 20 min, the sample was separated on a CAPCELL PAK CR （150 mm×2.0 m （I.d）, 5 μm） column using 5 mmol/L ammonium acetate （0.1% formic acid was added）-acetonilrile as mobile phase. The L-camitine was detected with positive-ion electrospray ionization mass spectrometry under multiple reaction monitoring （MRM） mode using （m/z） 162.2/103.2 and 162.2/85.1 as the quantitative and qualitative ions, respectively. A good linear calibration for L-carnitine was obtained in the range of 200-2 000 ng/mL with a correlation of 0.999 8. The detection limit for L-camitine was 97.5 μg/kg and the quantitation limit of the method was 0.33 mg/kg, The spiked recoveries were in the range of 98.2%- 106.5% （n=6）, RSD was 2.4%-3.2%. The results indicated that the method was rapid, senstitive and reproducible enough to examine L-camitine in mill powder.