离线SPE-LVI-GC-FID法分析婴儿配方奶粉中的饱和烃类矿物油

摘要

建立婴儿配方奶粉中饱和烃类矿物油(mineral oil saturated hydrocarbons,MOSH)的离线固相萃取(solid phase extraction,SPE)结合大体积进样-气相色谱-氢火焰离子化检测器(large volume injection-gas chromatography-flame ionization detection,LVI-GC-FID)的分析方法.该方法以正己烷为提取溶剂,提取液经硝酸银渍硅胶SPE柱净化;通过比较不同长径比SPE柱的净化效果,确定以5 mL玻璃注射器作为分离MOSH的SPE柱,收集洗脱液5mL,浓缩后注入LVI-GC-FID测定.GC的进样口升温程序为:初始温度45℃,保持1 min(分流比200∶1),以250℃/min升温至360℃(分流阀关闭2 min),并保持27 min(分流比为100∶1);柱温箱升温程序为:35℃保持3 min,以25℃/min升温至350℃,再以5℃/min升温至370℃,保持10 min;FID温度380℃;进样量40 μL.结果表明:MOSH的标准品液体石蜡在2～500 mg/kg范围内呈良好线性关系,相关系数为0.999,方法的定量限为0.05 mg/kg,加标回收率在92.62％～102.86％之间,相对标准偏差在0.85％～2.57％之间,适用于婴儿配方奶粉中MOSH的定量分析.应用该方法检测市售10种婴儿配方奶粉中的MOSH含量,其结果在0.24～1.30 mg/kg之间,其中MOSH (C16～C35)含量在0.12～0.85 mg/kg之间,表明有必要对婴儿配方奶粉中的矿物油污染进行监管.%An alternative method based on an off-line solid phase extraction (SPE) combined with large volume injection-gas chromatography-flame ionization detection (LVI-GC-FID) was developed to determine mineral oil saturated hydrocarbons (MOSH) in infant formula.The MOSH in samples were extracted with n-hexane.The extract was purified by solid phase extraction (SPE) on a column packed with silica gel impregnated silver nitrate and the optimal SPE cartridge was 5 mL glass syringe as indicated by comparison of different length to diameter ratios.Five milliliter of the pooled eluate was concentrated and then injected into the LVI-GC-FID system.The PTV parameters were as follows:the initial temperature was set at 45 ℃ and held for 1 min (split ratio was 200∶1),then increased to 360 ℃ at a linear gradient of 250 ℃/min and held for 27 min (split valve was closed for 2 min followed by split ratio of 100∶1).The GC column was heated from 35 ℃ (3 min) to 350 ℃ at 25 ℃/min,and then raised to 370 ℃ (10 min) at 5 ℃/min.FID temperature was set at 380 ℃.The GC injection volume was 40 μL.The calibration curve of paraffin oil was linear in the range of 2-500 mg/kg with correlation coefficient of 0.999.The quantification limit (LOQ) of MOSH in infant formula was 0.05 mg/kg.The recoveries from spiked samples were between 92.62％ and 102.86％,with relative standard deviation (RSD) of 0.85％-2.57％.This procedure was applied to analyze MOSH in 10 commercial infant formula samples and the contaminant levels ranged from 0.24 to 1.30 mg/kg (0.12-0.85 mg/kg of MOSH between C16 and C35).The results suggested that it is necessary to routinely detect mineral oil contamination in infant formula for infant health.