气相色谱-串联质谱法测定动物性食品中的9种N-亚硝胺类化合物

称取样品10.00g,加入100μL由N-二甲基亚硝胺-d6和N-亚硝基二丙胺-d14组成的混合内标溶液(1.00mg·L^-1),加入20mL乙腈,涡旋1min,于-20℃冷冻20min,再加入萃取盐(4g硫酸镁、1g氯化钠),迅速振荡30s,以8 000r·min^-1在0℃离心10min,取上清液加入10mL乙腈饱和的正己烷,涡旋1min,以6 000r·min^-1在0℃离心3min,去除正己烷层,加入净化填料(50mg N-丙基乙二胺、150mg封端十六烷基键合硅胶、900mg Na2SO4),涡旋1min,以8 000r·min^-1在0℃离心5min,取上清液用氮吹浓缩(不吹干),用乙腈定容至1.0mL,采用气相色谱-串联质谱法测定其中的9种N-亚硝胺类化合物。色谱分析中选用VF-WAXms色谱柱(0.25mm×30m,0.25μm),质谱中选择电子轰击离子源和多反应监测模式。9种N-亚硝胺类化合物的质量浓度在5.0~150μg·L^-1内与其峰面积呈线性关系,检出限为0.1μg·kg^-1,测定下限为0.5μg·kg^-1。加标回收率在89.0%~117%之间,测定值的相对标准偏差(n=6)在0.6%~8.0%之间。

Determination of Nine N-Nitrosamines in Animal Food by Gas Chromatography-Tandem Mass Spectrometry

10.00 g of the sample was taken,then 100μL of mixed internal standard solution(1.00 mg·L^-1,composed of N-nitrosodimethylamine-d6 and N-nitrosodi-n-propylamine-d14)and 20 mL of acetonitrile were added.After vortexing for 1 min,the mixture was freezed at-20 ℃ for 20 min.Then extract salt(4 g of magnesium sulfate,1 g of sodium chloride)was added,and the mixture was oscillated rapidly for 30 s,centrifuged at 8 000 r·min^-1 for 10 min at 0℃.The supernatant was taken and 10 mL of acetonitrile saturated n-hexane was added,and the mixture was vortexed for 1 min,centrifuged at 6 000 r·min^-1 for 3 min at 0 ℃.The n-hexane layer was removed,and purification packing material(50 mg of N-propyl ethylenediamine,150 mg of blocked octadecyl boned silica gel,900 mg of sodium sulfate)was added.After vortexing for 1 min and centrifuging at 8 000 r·min^-1 for 5 min at 0℃,the supernatant was concentrated by nitrogen blowing(not dry),and made up to 1.0 mL with acetonitrile.Nine N-nitrosamine compounds were determined by gas chromatography-tandem mass spectrometry.The VF-WAXms column(0.25 mm×30 m,0.25μm)was selected for chromatographic analysis.Electron impact ion source and multiple reaction monitoring mode were selected in mass spectrometry.Linear relationships were found between peak area and mass concentration of the nine N-nitrosamine compounds in the range of 5.0^-150μg·L^-1.The detection limits were 0.1μg·kg^-1,and the lower limits of determination were 0.5μg·kg^-1.Recovery obtained by standard addition method ranged from 89.0% to 117%,and the relative standard deviations(n=6)of the measured values ranged from 0.6%to 8.0%.