Museum Conservation Institute, Smithsonian Institution, Suitland, MD, USA.
Rapid Commun Mass Spectrom. 2014 Feb 15;28(3):305-10. doi: 10.1002/rcm.6786.
This paper introduces a novel ultrafast capillary electrophoresis (UFCE) mass spectrometry (MS) method comprised of a short (< 20 cm) and narrow (≤ 5 µm) capillary, with an integrated porous segment at the terminus of the capillary, for sheathless interfacing of CE to MS. The sheathless nature of the interface minimizes dead volume which is particularly important for ultrafast CE because of the small diameters of the capillaries.
The separation voltage across the capillary was set to produce an electric field of ≥1000 V/cm to provide an analysis time of approximately 1 min. For the analysis of peptides and protein digests, a background electrolyte containing 0.1% cationic polymer (polybrene or Poly-E) in 0.1% acetic acid in water was used to prevent analyte-wall interaction.
Uniquely, the porous tip of the capillary is adjustable. This allows the porous tip to be pulled inside the sheath liquid for sample stacking during injection, or sample focusing in isoelectric focusing (IEF), or, alternatively, pushed outside of the sheath liquid for electrospray ionization (ESI). The adjustable interface preserves electrical conductivity during electrokinetic injection with reverse electro-osmotic flow. Therefore, pre-concentration of analytes at the capillary inlet is achieved without the need to disassemble the interface, improving the throughput.
As a proof of concept, the application of UFCE-MS was demonstrated by the analysis of a peptide mixture and a protein digest in ~1 min.
本文介绍了一种新颖的超快毛细管电泳（UFCE）-质谱（MS）方法，该方法采用短（<20 cm）、窄（≤5 µm）的毛细管，并在毛细管末端集成了一个多孔段，用于无鞘液 CE 与 MS 的接口。该接口的无鞘液性质最小化了死体积，这对于超快 CE 尤为重要，因为毛细管的直径很小。
在毛细管上施加的分离电压设定为产生≥1000 V/cm 的电场，以提供大约 1 分钟的分析时间。对于肽和蛋白质消化物的分析，使用含有 0.1%阳离子聚合物（聚胺或 Poly-E）的背景电解质在水中，以 0.1%的乙酸，以防止分析物与管壁相互作用。
独特的是，毛细管的多孔尖端是可调节的。这允许在进样过程中将多孔尖端拉入鞘液中进行样品堆积，或在等电聚焦（IEF）中进行样品聚焦，或者将其推出鞘液外进行电喷雾电离（ESI）。可调接口在带有反向电渗流的电动进样过程中保持电导率，因此无需拆卸接口即可实现分析物在毛细管入口处的预浓缩，提高了通量。
作为概念验证，通过在大约 1 分钟内分析肽混合物和蛋白质消化物，展示了 UFCE-MS 的应用。
