银离子固相萃取-程序升温大体积进样-气相色谱法定量分析市售巧克力中的饱和烷烃矿物油

Ag-Solid-Phase Extraction-Programmed Temperature Vaporization-Gas Chromatography for Analysis of Mineral Oil-Saturated Hydrocarbons in Commercial Chocolates

建立了银渍硅胶固相萃取柱离线(Ag-SPE)净化,程序升温进样-气相色谱-氢火焰离子化检测器(PTV-GC-FID)定量分析巧克力中饱和烷烃矿物油(MOSH)的方法。以正己烷浸泡提取巧克力中的MOSH,离心后取1 mL上清液,过0.3%Ag渍硅胶SPE柱净化,氮吹浓缩,定容至0.2 mL,注入GC分析;GC的进样口程序升温过程: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100∶1);进样量40μL;柱温箱升温程序为:35℃保持3 min,以25℃/min升温至350℃,以5℃/min升温至370℃,保持10 min,载气为高纯氮气,流速1.3 mL/min(压力60 k Pa);FID温度为380℃。结果表明,本方法的MOSH定量限为0.5 mg/kg,加标回收率为84.9%~108.6%,相对标准偏差(RSD)为0.2%~1.5%。运用本方法对25个市售巧克力样品中的MOSH含量进行了测定,3个样品未检出,其余22个样品中MOSH含量为1.09~8.15 mg/kg(其中C_(16)~C_(35)的含量为0.56~4.43 mg/kg),有3个样品含量高于5.00 mg/kg,为严重污染样品。本方法操作简便,检出限低,适用于巧克力中MOSH的定量测定。

An offline silver-impregnated silica gel solid-phase extraction(Ag-SPE)approach combined with aprogrammed temperature vaporization-gas chromatography-flame ionization detector(PTV-GC-FID)wasproposed for routine analysis of mineral oil saturated hydrocarbons(MOSH)in chocolates.The MOSH inchocolates were extracted by n-hexane and1mL of extract was purified by offline Ag-SPE column.The SPEcolumns packed with0.3%Ag-activated silica gel were used to separate MOSH from triglycerides and olefinsin chocolates.The eluent of MOSH fraction was only5mL and then concentrated to0.2mL through nitrogenblowing with little evaporation loss.The PTV parameters were as follows:the initial temperature was set at45益and held for1min(split ratio was200颐1),then warmed up to360益at linear gradient of250益min1and held for27min(split valve was closed for2min followed by split ratio of100颐1).The GC injectionvolume was40滋L.The GC column was heated from35益(3min)to350益at25益/min,and then raised to370益(10min)at5益/min.The flow rate of the carrier gas was1.3mL/min(and pressure was60kPa),FID temperature was set at380益.The limit of quantification(LOQ)and the recoveries of the method were0.5mg/kg and84.9%-108.6%,respectively,with the relative standard deviations(RSD)of0.2%-1.5%.Twenty-five commercial chocolate samples were analyzed with the proposed method,and it was foundthat the MOSH in three samples were not detected,and the concentrations of MOSH in other22samples were1.09-8.15mg/kg(the concentrations of MOSH with C^-C35component were0.56-4.43mg/kg).Theresults suggested that it was necessary to routinely detect mineral oil contamination in chocolates for foodsafety.