Institute of Quality Standard and Monitoring Technology for Agro-products, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China; Key Laboratory of Testing and Evaluation for Agro-product Safety and Quality, Ministry of Agriculture and Rural Affairs, Guangzhou 510640, China; Laboratory of Quality & Safety Risk Assessment For Agro-products (Guangzhou), Ministry of Agriculture and Rural Affairs, Guangzhou 510640, China.
Institute of Quality Standard and Monitoring Technology for Agro-products, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China.
J Chromatogr A. 2021 Apr 12;1642:462002. doi: 10.1016/j.chroma.2021.462002. Epub 2021 Feb 18.
The formation of halide adducts ion is an important pathway to improve the sensitivity of analytes in liquid chromatography (LC) combined with negative electrospray ionization (ESI) mass spectrometry (MS). Although adding modifier in mobile phase is generally the simplest way to form anions adducts, the formation of halide adducts ion requires a complex post-column addition strategy since traditional halide ionization enhancement reagents are incompatible with LC systems. To solve this problem, the volatile organochlorine salt tetramethyl ammonium chloride (TMAC) was therefore investigated as a potentially non-corrosive mobile phase modifier that was confirmed to be compatible with both LC and MS systems in this study. When short-chain, medium-chain, and long-chain chlorinated paraffins (CPs) were determinated simultaneously by ultra-high performance LC combined with ESI high resolution MS (UPLC-ESI-HRMS), all of them tended to ionize by forming [M+Cl] ions and exhibited excellent sensitivity with the instrumental detection limits of 1-4 pg/μL. Meanwhile, their sensitivities towards CPs were less dependent on their Cl content with the total relative response factors of 0.8-3.5. The method's utility was demonstrated through determination of CPs in surface soil and chicken muscle samples. This was an effective and practical method to enhance the selectivity for [M + Cl] ions and improve sensitivity towards CPs with various carbon lengths. Importantly, post-column addition was not required, and thus the analytical procedure was simplified. The method has also improved sensitivity towards some other organohalides and may be generally useful in the determination of challenging organic analytes.
形成卤化物加合物离子是提高液相色谱（LC）与负电喷雾电离（ESI）质谱（MS）联用分析物灵敏度的重要途径。虽然在流动相中添加修饰剂通常是形成阴离子加合物的最简单方法，但由于传统的卤化物离子增强试剂与 LC 系统不兼容，因此需要一种复杂的柱后添加策略来形成卤化物加合物离子。为了解决这个问题，本研究因此考察了挥发性有机氯盐四甲基氯化铵（TMAC）作为一种潜在的非腐蚀性流动相修饰剂，它被证实与 LC 和 MS 系统均兼容。当短链、中链和长链氯化石蜡（CPs）同时通过超高效 LC 与 ESI 高分辨 MS（UPLC-ESI-HRMS）进行测定时，它们都倾向于通过形成[M+Cl]离子而离子化，并且具有出色的灵敏度，仪器检测限为 1-4 pg/μL。同时，它们对 CPs 的灵敏度与其氯含量的相关性较小，总相对响应因子为 0.8-3.5。该方法通过测定土壤表面和鸡肉样品中的 CPs 验证了其实用性。这是一种有效且实用的方法，可以增强对[M+Cl]离子的选择性，并提高对各种碳长的 CPs 的灵敏度。重要的是，不需要柱后添加，从而简化了分析程序。该方法还提高了对其他一些有机卤化物的灵敏度，可能在测定具有挑战性的有机分析物方面具有普遍的应用价值。
