建立了巧克力中饱和烃类矿物油的离线固相萃取(solid phase extraction,SPE)结合气相色谱-氢火焰离子化检测器(gas chromatography-flame ionization detection,GC-FID)的分析方法。以正己烷为提取溶剂,提取液经装有0.3%(质量分数)硝酸银硅胶的玻璃SPE柱净化,GC-FID测定。GC进样口温度275 ℃;柱温箱升温程序为:50 ℃,以2.5 ℃/min升温至60 ℃,再以22 ℃/min升温至280 ℃,以30 ℃/min升温至320 ℃,保持12 min;FID温度350 ℃;进样量2 μL。结果表明,饱和烃矿物油标准品在1~80 mg/kg线性关系良好,相关系数为0.999;方法的定量限为0.5 mg/kg;加标回收率在90.0%~99.2%,相对标准偏差在6.1%~9.9%。该方法准确度、精密度和灵敏度均符合饱和烃类矿物油检测的要求,可用于巧克力中饱和烃类矿物油污染的监管。
An alternative method based on an off-line solid phase extraction (SPE) combined with gas chromatography-flame ionization detection (GC-FID) method was developed to determine mineral oil saturated hydrocarbons (MOSH) in Chocolate. The MOSH was extracted with n-hexane. The extract was purified by solid phase extraction (SPE) on a column packed with silica gel impregnated silver nitrate. By comparing the purification effect of silica gel with different silver nitrate content, 0.3% (w/w) silver nitrate silica gel was determined to be the best, and a glass syringe was used as the container for filling silver nitrate silica gel, and the volume of eluent was determined to be 10 mL. The pooled eluate was concentrated and then injected into the GC-FID system. The inject temperature was 275 ℃. The GC column was heated from 50 ℃ to 60 ℃ at 2.5 ℃/min, and then raised to 280 ℃ at 22 ℃/min,and then raised to 320 ℃(12 min) at 30 ℃/min. FID temperature was set at 350 ℃. The GC injection volume was 2 μL. The results showed that the calibration curve of paraffin oil was linear in the range of 1-80 mg/kg with a correlation coefficient of 0.999. The quantification limit (LOQ) of MOSH in chocolate was 0.5 mg/kg. The recoveries from spiked samples were between 90.0% and 99.2%, with the relative standard deviation (RSD) of 6.1%-9.9%. The accuracy, precision and sensitivity of the method are in line with the requirements of saturated hydrocarbon mineral oil detection, and can be used for monitoring the contamination of saturated hydrocarbon mineral oil in chocolate.
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