食品中有机氯农药和多氯联苯气相色谱-质谱分析的离子化方式

Different Ionization Modes in Gas Chromatography-Mass Spectrometric Determination of Organochlorine Pesticides and Polychlorinated Biphenyls in Food

对食品中有机氯农药和多氯联苯的气相色谱-质谱联用(GC-MS)分析方法中三种离子化方式,电子轰击电离(EI)、正化学电离(PCI)和负化学电离(NCI)进行了总结和比较。PCI-MS/MS方法和EI-MS/MS方法都有很高的选择性和较高的灵敏度;PCI方法在分析含硝基、羰基等基团的化合物时有明显优势,EI则在分析狄氏剂、异狄氏剂、硫丹及其代谢物时比PCI表现稍好,而NCI-MS的灵敏度最高,但抗干扰能力稍弱,且不适合分析滴滴涕类和多氯联苯类化合物。在食品安全分析中,三种质谱方法的准确性好,精密度高,检测限较低,都能够满足食品中农残检测的要求,在日常检测工作中可互为补充和替代。同时指出,GC在有机氯化合物分析中仍表现出明显的优越性;常规的GC-MS尤其在EI电离模式下,易受到基质干扰而使谱图变得复杂;新型离子化方式包括高选择性化学电离技术的应用,将是食品安全中GC-MS联用分析的发展方向之一。

Different modes of electron impact （EI）, positive chemical ionization （PCI） and negative chemical ionization （NCI） in Gas Chromatography-Mass Spectrometry （GC-MS） determination of organochlorine pesticides （OCPs） and polychlorinated biphenyls （PCBs） in food are summarized and compared in this paper. Both PCI-MS/ MS and El-MS/MS have high selectivity and sensitivity. PCI-MS/MS has obvious advantages in the analysis of compounds containing nitro or carbonyl groups, while El-MS/MS has slightly better performance when dealing with dieldrin, endrin, endosulfan and its metabolites. NCI-MS has the highest sensitivity, but weaker anti-interference ability, and is not suitable for the analysis of DDTs and PCBs. In summary, these three mass spectrometry methods, which are complementary and alternative to the routine analysis, can satisfy the requirements of pesticide residue analysis in food by providing good accuracy, good precision and low detection limits. Also it points out that Gas Chromatography showed a superiority in organochlorine compound analysis, but for traditional GC-MS, especially in the EI ionization mode, the spectrum is more complicated because of matrix interference. New ionization modes including the highly selective chemical ionization, will be one of future developments and trends of Gas Chromatography applications in the field of food safety analysis.