Abstract

Supercritical fluid chromatography (SFC) is a promising alternative to conventional chromatographic methods and has several advantages over them in selectivity, efficiency, speed of separation, and environmental friendliness. Its combination with atmospheric pressure chemical ionization (APCI) mass spectrometric detection is one of the central areas of method development and requires an understanding of the APCI specificity in using carbon dioxide-based mobile phases. In the present study, the composition of negatively charged ions formed under APCI conditions for carbon dioxide–organic modifier (methanol, isopropanol, acetonitrile) systems, and also the influence of the mobile phase and ion source parameters (corona discharge needle voltage, temperature) on it are studied using high-resolution mass spectrometry. The results obtained testify to a significant role of carbon dioxide as a direct precursor for the formation of reaction particles (hydrocarbonate and percarbonate anions, carbonate radical anion) and as a reagent capable of shifting the ion-molecular equilibrium in corona discharge plasma and forming compounds with the organic modifier (alkylcarbonic acid anions in the case of alcohols, adduct with a deprotonated acetonitrile molecule). Ion-molecular equilibria involving carbon dioxide result in the formation of a large number of reactive particles that can take part in the ionization processes of analytes in SFC–APCI-MS.

中文翻译：

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大气压化学电离超临界流体色谱-质谱法：流动相组分的负电荷离子

摘要

超临界流体色谱 ( SFC ) 是传统色谱方法的一种有前景的替代方法，在选择性、效率、分离速度和环境友好方面比传统色谱方法具有多种优势。其与大气压化学电离 ( APCI ) 质谱检测的结合是方法开发的核心领域之一，需要了解使用二氧化碳流动相时的 APCI 特异性。本研究研究了二氧化碳-有机改性剂（甲醇、异丙醇、乙腈）体系在APCI条件下形成的带负电离子的组成，以及流动相和离子源参数（电晕放电针电压、温度）的影响使用高分辨率质谱对其进行研究。获得的结果证明二氧化碳作为反应颗粒（碳酸氢根和过碳酸盐阴离子、碳酸根阴离子）形成的直接前体以及作为能够改变电晕放电等离子体中的离子-分子平衡并形成化合物的试剂发挥着重要作用与有机改性剂（在醇的情况下为烷基碳酸阴离子，与去质子化的乙腈分子的加合物）。涉及二氧化碳的离子-分子平衡导致形成大量反应颗粒，这些颗粒可以参与 SFC-APCI-MS 中分析物的电离过程。