固相萃取-气相色谱-质谱联用检测地沟油中胆固醇

Determination of cholesterol in drainage oil by solid phase extraction-gas chromatography-mass spectrometry

建立了固相萃取-气相色谱-质谱联用(SPE-GC-MS)检测地沟油样品中胆固醇的分析方法。样品用硅胶固相萃取小柱前处理净化,先用20 mL含0.6%乙醚的正己烷溶液淋洗,再用10 mL含15%乙醚的正己烷溶液洗脱,胆固醇萃取率达97%。净化后的样品用配备电子轰击离子源的气相色谱-质谱联用仪进行测定,以保留时间和特征碎片离子定性,在选择离子监测模式下用外标法定量,选择离子为m/z 213、275、301、368、386,目标离子为m/z 386,参考离子为m/z 213和275。不同加标水平下的加标回收率为91.7%～101%,相对标准偏差(RSD)小于6%,检出限为0.01 mg/L。胆固醇质量浓度在0.24～6.0 mg/L范围内有良好的线性关系(相关系数为0.999 6)。该法可精确检测油脂中胆固醇的含量,检测结果可作为判断其中是否掺有地沟油的依据之一。

An effective method was developed for the determination of cholesterol in drainage oil by solid phase extraction-gas chromatography-mass spectrometry（SPE-GC-MS）.Firstly,the samples were purified by SPE on a column packed with silica.An extraction yield of 97% was obtained when a 20 mL of ethyl ether/n-hexane mixture（0.6∶99.4,v/v） was used for washing the SPE column,and 10 mL of the same solvent mixture（15∶85,v/v） for desorbing cholesterol from the SPE column.Then the final extract was determined by GC-MS with electron impact ion source.The cholesterol was characterized according to retention time and characteristic fragments（m/z 213,275,301,368,386）,and was quantitatively determined by external standard method in selected ion monitoring mode.The fragment of m/z 386 was selected as the target ion,and m/z 213 and m/z 275 were used as the reference ions.The average recovery was from 91.7% to 101%,and the relative standard deviations（RSDs） were below 6%,and the detection limit was 0.01 mg/L.A good linearity was obtained in the cholesterol concentration range of 0.24-6.0 mg/L with the correlation coefficient of 0.999 6.The proposed method can be used to determine the cholesterol content in oil accurately,and the detection result can be one of the criteria judging the existence of drainage oil in edible oil.