同位素稀释-超高效液相色谱-串联质谱技术分析婴儿配方奶粉中的维生素D

为了准确测定婴儿配方奶粉中维生素D的含量，建立了同位素稀释-超高效液相色谱-串联质谱联用技术分析维生素D含量的方法。样品经氢氧化钾皂化，用V（正戊烷）∶V（乙醚）=4∶1的混合溶液提取，采用Waters T₃色谱柱分离，以2 mmol/L甲酸铵-甲醇和2 mmol/L甲酸铵-水溶液为流动相进行梯度洗脱，采用电喷雾-正离子电离源多反应监测模式进行定性和定量分析，内标法定量。维生素D₂和维生素D₃在5～150 μg/L质量浓度范围内线性关系良好，维生素D₂和维生素D₃的检出限均为1.5 μg/kg，定量限均为5.0 μg/kg，方法回收率分别为97.0%～104.7%和92.7%～108.0%，日内和日间相对标准偏差均小于10%。该方法简单、灵敏度高、分析时间短、定量准确，适用于婴儿奶粉中维生素D的测定。

Determination of Vitamin D in Infant Milk Powder by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry with Isotopes Dilution

In order to establish a reliable method for quantitative analysis of vitamin D in infant milk powder, a ultra performance liquid chromatography-tandem mass spectrometry (UPLC/MS/MS) with isotopes dilution method was developed. The samples were saponifed with KOH and extracted by pentane-ethyl ether solution (V(pentane)∶V(ethyl ether)=4∶1). The target analytes were separated on the Waters T₃ column with gradient elution using methanol and water (containing 2 mmol/L ammonium formate for both) as mobile phase. The identification and quantification were achieved by using electrospray ionization in positive ion mode and with multiple reaction monitoring. Internal standard method was used to determine the results. The linear range of the calibration curve was 5—150 μg/L. The limit of detection (LOD) of the method was 1.5 μg/kg, and the limit of quantitation (LOQ) was 5.0 μg/kg. The recoveries of the method were in the range of 97.0%—104.7% and 92.7%—108.0% for vitamin D₂ and vitamin D₃ respectively. The relative standard deviations (RSD) of intra-day and inter-day were less than 10%. The simply, rapid, accurate and sensitive method can be applied to determine the vitamin D in infant milk powder.