Nanoflow Sheath Voltage-Free Interfacing of Capillary Electrophoresis and Mass Spectrometry for the Detection of Small Molecules,Analytical Chemistry

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Nanoflow Sheath Voltage-Free Interfacing of Capillary Electrophoresis and Mass Spectrometry for the Detection of Small Molecules
Analytical Chemistry ( IF 6.7 ) Pub Date : 2022-08-01 , DOI: 10.1021/acs.analchem.2c02074
Yousef S Elshamy ₁ , Timothy G Strein ₂ , Lisa A Holland ₁ , Chong Li ₁ , Anthony DeBastiani ₁ , Stephen J Valentine ₁ , Peng Li ₁ , John A Lucas ₁ , Tyler A Shaffer ₁

Affiliation

Coupling capillary electrophoresis (CE) to mass spectrometry (MS) is a powerful strategy to leverage a high separation efficiency with structural identification. Traditional CE-MS interfacing relies upon voltage to drive this process. Additionally, sheathless interfacing requires that the electrophoresis generates a sufficient volumetric flow to sustain the ionization process. Vibrating sharp-edge spray ionization (VSSI) is a new method to interface capillary electrophoresis to mass analyzers. In contrast to traditional interfacing, VSSI is voltage-free, making it straightforward for CE and MS. New nanoflow sheath CE-VSSI-MS is introduced in this work to reduce the reliance on the separation flow rate to facilitate the transfer of analyte to the MS. The nanoflow sheath VSSI spray ionization functions from 400 to 900 nL/min. Using the new nanoflow sheath reported here, volumetric flow rate through the separation capillary is less critical, allowing the use of a small (i.e., 20 to 25 μm) inner diameter separation capillary and enabling the use of higher separation voltages and faster analysis. Moreover, the use of a nanoflow sheath enables greater flexibility in the separation conditions. The nanoflow sheath is operated using aqueous solutions in the background electrolyte and in the sheath, demonstrating the separation can be performed under normal and reversed polarity in the presence or absence of electroosmotic flow. This includes the use of a wider pH range as well. The versatility of nanoflow sheath CE-VSSI-MS is demonstrated by separating cationic, anionic, and zwitterionic molecules under a variety of separation conditions. The detection sensitivity observed with nanoflow sheath CE-VSSI-MS is comparable to that obtained with sheathless CE-VSSI-MS as well as CE-MS separations with electrospray ionization interfacing. A bare fused silica capillary is used to separate cationic β-blockers with a near-neutral background electrolyte at concentrations ranging from 1.0 nM to 1.0 μM. Under acidic conditions, 13 amino acids are separated with normal polarity at a concentration ranging from 0.25 to 5 μM. Finally, separations of anionic compounds are demonstrated using reversed polarity under conditions of suppressed electroosmotic flow through the use of a semipermanent surface coating. With a near-neutral separation electrolyte, anionic nonsteroidal anti-inflammatory drugs are detected over a concentration range of 0.1 to 5.0 μM.

中文翻译：

用于检测小分子的毛细管电泳和质谱的纳流鞘无电压接口

将毛细管电泳 (CE) 与质谱 (MS) 耦合是利用高分离效率和结构鉴定的强大策略。传统的 CE-MS 接口依靠电压来驱动该过程。此外，无鞘接口要求电泳产生足够的体积流量以维持电离过程。振动锐边喷雾电离 (VSSI) 是将毛细管电泳与质量分析仪连接的新方法。与传统接口相比，VSSI 是无电压的，因此可以直接用于 CE 和 MS。这项工作引入了新的纳流鞘CE-VSSI-MS，以减少对分离流速的依赖，以促进分析物转移到MS。纳流鞘 VSSI 喷雾电离功能范围为 400 至 900 nL/min。使用本文报道的新的纳流鞘，通过分离毛细管的体积流速不太重要，允许使用小内径（即20至25μm）的分离毛细管，并能够使用更高的分离电压和更快的分析。此外，纳米流鞘的使用使得分离条件具有更大的灵活性。纳米流鞘使用背景电解质和鞘中的水溶液进行操作，证明在存在或不存在电渗流的情况下可以在正常和反向极性下进行分离。这还包括使用更宽的 pH 范围。通过在各种分离条件下分离阳离子、阴离子和两性离子分子，证明了纳流鞘 CE-VSSI-MS 的多功能性。使用纳流鞘 CE-VSSI-MS 观察到的检测灵敏度与使用无鞘 CE-VSSI-MS 以及电喷雾电离接口的 CE-MS 分离获得的检测灵敏度相当。裸露的熔融石英毛细管用于分离浓度范围为 1.0 nM 至 1.0 μM 的阳离子 β-阻滞剂和近中性背景电解质。在酸性条件下，13 个氨基酸以正常极性在 0.25 至 5 μM 的浓度范围内分离。最后，通过使用半永久性表面涂层，在抑制电渗流的条件下，使用反极性证明了阴离子化合物的分离。使用接近中性的分离电解质，可检测浓度范围为 0.1 至 5.0 μM 的阴离子非甾体抗炎药。

更新日期：2022-08-01

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