Freie Universität Berlin, Institute of Pharmacy, Königin-Luise-Str. 2+4, 14195 Berlin, Germany.
Agilent Technologies GmbH, Hewlett-Packard-Str. 8, 76337 Waldbronn, Germany.
J Chromatogr B Analyt Technol Biomed Life Sci. 2018 Aug 1;1091:67-78. doi: 10.1016/j.jchromb.2018.05.017. Epub 2018 May 16.
A systematic evaluation of splitless hyphenation of supercritical fluid chromatography (SFC) with mass spectrometry (MS) was performed using different techniques for ambient pressure ionization. Interfaces commonly known from HPLC-MS/MS, i.e. electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photo ionization (APPI), were tested for their suitability in SFC-MS/MS. A triple quadrupole MS was used for data evaluation in a targeted multi-analyte design using endogenous steroids as model compounds. Individual optimization of the ionization parameters was performed in multi-dimensional design for best support of ionization in all three techniques. A post-column make-up was used to avoid analyte precipitation in the transfer capillary but also to support ionization independently from mobile phase composition. Buffer choice and concentration as well as temperature were found crucial in ESI and APCI. Best results for the multi-analyte method were obtained in both techniques using ammonium fluoride as make-up buffer. Instead of buffer solutions different organic solvents were used as dopants in APPI to support ionization. The mobile phase constituent isopropanol was already found to support ionization in APPI, however, for many analytes the addition of toluene resulted in superior results in terms of intensity. Comparing the optimized methods in terms of limit of detection (LOD), limit of quantification (LOQ), and sensitivity (slope of calibration curve) ESI was the best choice for the multiple analyte design. Only a few analytes resulted in a different optimum ionization, if focused on separately. In terms of linear dynamic range, APCI and APPI proved superior to ESI, where calibration over the whole range of concentrations (from LOD up to 5000 pg ∗ μL) required quadratic regression.
采用不同的大气压离子化技术对超临界流体色谱（SFC）与质谱（MS）的不分流连接进行了系统评价。对 HPLC-MS/MS 中常见的接口，即电喷雾电离（ESI）、大气压化学电离（APCI）和大气压光电离（APPI），进行了适用性测试，以用于 SFC-MS/MS。使用三重四极杆 MS 以靶向多分析物设计对数据进行评估，以内源性甾体为模型化合物。在多维设计中对离子化参数进行单独优化，以在所有三种技术中最佳支持离子化。采用柱后补加以避免在传输毛细管中出现分析物沉淀，但也可以独立于流动相组成支持离子化。发现缓冲液选择和浓度以及温度在 ESI 和 APCI 中至关重要。使用氟代铵作为补加缓冲液，在这两种技术中均获得了多分析物方法的最佳结果。而不是缓冲溶液，在 APPI 中使用不同的有机溶剂作为掺杂剂来支持离子化。已经发现异丙醇作为流动相成分可以在 APPI 中支持离子化，但是对于许多分析物，添加甲苯会导致强度方面的优异结果。就检测限（LOD）、定量限（LOQ）和灵敏度（校准曲线斜率）而言，对优化后的方法进行比较，ESI 是多分析物设计的最佳选择。如果单独关注，则只有少数分析物会得到不同的最佳离子化。在线性动态范围内，APCI 和 APPI 优于 ESI，ESI 要求在整个浓度范围内（从 LOD 到 5000 pg*μL）进行二次回归。
