Koerner Terry, Turck Kiera, Brown Laurie, Oleschuk Richard D
Department of Chemistry, Queen's University, Kingston, Ontario, Canada K7L 3N6.
Anal Chem. 2004 Nov 1;76(21):6456-60. doi: 10.1021/ac049438y.
Coupling low-flow analytical separation instrumentation such as capillary electrophoresis, capillary electrochromatography, nano-HPLC, and microfluidic-based devices with electrospray ionization mass spectrometry has yielded powerful analytical tools. However, conventional coupling methodologies such as nanospray suffer from limitations including poor conductive coating robustness, constant clogging, complicated fabrication processes, and incompatibility with large flow rate regimes. This study demonstrates that robust nanospray emitters can be fabricated through the formation and utilization of a porous polymer monolith (PPM) at the end of a fused-silica capillary. Stable electrosprays can be produced from capillaries (75-100-microm i.d.) at a variety of flow rates (50-1000 nL/min) without the need to taper the capillaries by etching or pulling. The PPM is photopatterned to be present only near the capillary exit aperture using conditions that generate pore sizes similar to those seen with nanospray tips. The porous nature of the PPM aids in developing a stable electrospray generating a single clearly visible Taylor cone at relatively high flow rates while at low flow rates (<100 nL/min) a mist, presumably from multiple small Taylor cones, develops. The hydrophobic nature of the PPM should limit problems with band broadening associated with droplet spreading at the capillary exit, while the multiple flow paths inherent in the PPM minimize clogging problems associated with conventional nanospray emitters. Total ion current traces for a constant infusion of standard PPG and cytochrome c solutions are very stable with deviations ranging from only 3 to 8%. The PPM-assisted electrospray produces mass spectra with excellent signal-to-noise ratios from only a few femtomoles of material.
将低流量分析分离仪器（如毛细管电泳、毛细管电色谱、纳米高效液相色谱和基于微流控的设备）与电喷雾电离质谱联用，已产生了强大的分析工具。然而，传统的联用方法（如纳米喷雾）存在局限性，包括导电涂层稳定性差、持续堵塞、制造工艺复杂以及与大流速范围不兼容。本研究表明，通过在熔融石英毛细管末端形成并利用多孔聚合物整体柱（PPM），可以制造出坚固的纳米喷雾发射器。在各种流速（50 - 1000 nL/min）下，可从内径为75 - 100微米的毛细管产生稳定的电喷雾，无需通过蚀刻或拉伸使毛细管变细。使用产生与纳米喷雾尖端类似孔径的条件，对PPM进行光图案化处理，使其仅存在于毛细管出口孔附近。PPM的多孔性质有助于形成稳定的电喷雾，在相对较高流速下产生单个清晰可见的泰勒锥，而在低流速（<100 nL/min）下会形成雾，推测是由多个小泰勒锥产生的。PPM的疏水性质应能限制与毛细管出口处液滴扩散相关的谱带展宽问题，而PPM固有的多条流动路径可将与传统纳米喷雾发射器相关的堵塞问题降至最低。对于标准聚丙二醇（PPG）和细胞色素c溶液的恒流注入，总离子流曲线非常稳定，偏差范围仅为3%至8%。PPM辅助电喷雾仅从几飞摩尔的材料就能产生具有出色信噪比的质谱图。
