气相色谱-质谱联用-负化学源法测定食品中指示性多氯联苯的研究

Determination of Polychlorinated Biphenyls(PCBs) in Foodstuffs by GC-MS-NCI Coupled with Isotope Dilution Technique

[目的]以加速溶剂萃取技术和稳定性同位素稀释法、气相色谱负化学源（NCI）质谱法，建立食品中指示性多氯联苯单体（PCBs）测定方法。[方法]样品中加入^13C12取代同位素，经加速溶剂萃取、浓缩、混合硅胶柱与氧化铝柱净化后，以GC—MS-NCI分析浓缩液，进行选择离子监测，以内标法的相对响应因子定量。[结果]各单体在20～2000ng／mL内重复测定时，相对响应因子的相对标准偏差（RSD）2．2％～19．3％，符合线性要求；检测限0．003～38．6μg／kg，同时低于5个氯原子的PCBs单体，其NCI法灵敏度小于EI法，当超过5个氯原子时，NCI法灵敏度为EI法的1．1～67．4倍；以干贝与肉松为加标基质进行准确度和精密度试验，干贝加标水平为0．5、1．0μg／kg，肉松为0．5μg／kg。测定国家限量标准规定的PCBs各单体时，其回收率和RSD分别在72．1％～129％和4．1％～18．5％。[结论]本法测定PCBs的灵敏度较高，可满足国家限量标准的要求。

[Objective] To establish a method for determination of indicator polychlorinated biphenyls （PCBs） in food- stuffs by gas chromagrgraphy-mass spectrometer with negative chemical ionization （GC-MS-NCI）. [Methods] The stable isotope internal standard was added into the sample and the mixture was extracted by accelerated solvent extraction （ASE） method. The extract was cleaned up by multilayer silica column and alumina column. The concentrated element was analyzed by GC-MS-NCI with the selection monitoring mode. [Results] The relative standard deviations （RSD） of the relative response factor of the PCBs indicator was in 2.2%-19.30% detected in 20-2 000 ng/mL for standard solution. The limit of detection by NCI method was in 0. 003-38.6 μg/kg, which was lower than that by electron ionization （EI） except the PCBs indicator containing the number of chloride lower than 5. In the matrix of seafood and meat products, recovery and RSD of the PCBs indicator involved in the national standard were in the range of 72.1 %-129 % and 4.1 %-18.5%, respectively. [Conclusion] The developed method is suitable for the determination of the indicator PCBs required in toler ance standard for foodstuffs in China.