On-column sample enrichment for capillary electrophoresis sheathless electrospray ionization mass spectrometry: evaluation for peptide analysis and protein identification |
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Authors: | Janini George M Zhou Ming Yu Li-Rong Blonder Josip Gignac Michelle Conrads Thomas P Issaq Haleem J Veenstra Timothy D |
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Affiliation: | Laboratory of Proteomics and Analytical Technologies and Image Analysis Laboratory, SAIC-Frederick, Inc., National Cancer Institute at Frederick, P.O. Box B, Frederick, Maryland 21702, USA. Janini@mail.ncifcrf.gov |
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Abstract: | Although several designs have been advanced for coupling sample enrichment devices to a sheathless electrospray ionization-mass spectrometry (MS) interface on a capillary electrophoresis (CE) column, most of these approaches suffer from difficulties in fabrication, and the CE separation efficiency is degraded as a result of the presence of coupling sleeves. We have developed a design that offers significant improvements in terms of ease of fabrication, durability, and maintenance of the integrity of the CE-separated analyte zones. Capillaries with different inside and outside diameters were evaluated to optimize the performance of the CE-MS system, resulting in a mass limit of detection of 500 amol for tandem MS analysis of a standard peptide using a 20-microm-i.d. capillary. The improved design incorporates an efficient method to preconcentrate a sample directly within the CE capillary followed by its electrophoretic separation and detection using a true zero dead-volume sheathless CE-MS interface. Testing of this novel CE-MS system showed its ability to characterize proteomic samples such as protein digests, in-gel-digested proteins, and hydrophobic peptides as well as to quantitate ICAT-labeled peptides. |
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