On-line coupling of SPE and CE-MS for peptide analysis

• Published in: Electrophoresis Vol. 28; no. 9; pp. 1319 - 1326
• Main Authors: Tempels, F. W. Alexander, Underberg, Willy J. M., Somsen, Govert W., de Jong, Gerhardus J.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.05.2007; WILEY‐VCH Verlag
• Subjects: Cerebrospinal fluid; Electrophoresis, Capillary - instrumentation; Electrophoresis, Capillary - methods; Enkephalins - cerebrospinal fluid; Feasibility Studies; In-line valve interface; Logical Observation Identifiers Names and Codes; Peptides - analysis; Proteins - analysis; Proteomics - methods; Reproducibility of Results; Sensitivity and Specificity; Solid Phase Extraction - instrumentation; Solid Phase Extraction - methods; SPE; Spectrometry, Mass, Electrospray Ionization - instrumentation; Spectrophotometry, Ultraviolet; Systems Integration
• ISSN: 0173-0835; 1522-2683
• DOI: 10.1002/elps.200600403

An on‐line SPE‐CE‐MS system has been developed for the analysis of peptides. Analytes are preconcentrated using a C18 microcolumn (5×0.5 mm id), and then introduced into the CE system via a valve interface. The CE system with a Polybrene‐poly(vinylsulfonate) bilayer coated capillary is combined with an ion‐trap mass spectrometer via ESI using a coaxial sheath‐liquid sprayer. The on‐line coupling of the SPE and CE step by the valve interface is advantageous because it allows an independent functioning of the system parts. Optimization of the SPE‐CE system was performed using UV detection. Subsequently, the SPE‐CE system has been coupled to the ion‐trap mass spectrometer. Test solutions with enkephalin peptides (50 ng/mL) were used for evaluation of system performance. Repeatability of effective mobility and peak area ratio of the two enkephalins were within 1.2% and 9% RSD, respectively. The analysis of 1:1 v/v diluted cerebrospinal fluid samples spiked with enkephalin peptides showed detection limits (S/N = 3) in the range of 1.5–3 ng/mL (around 5 nM), which were similar to those obtained for enkephalin test solutions. Moreover, the potential of the on‐line SPE‐CE‐MS system was demonstrated by the analysis of a cytochrome C digest. Some hydrophilic peptides did not show sufficient retention on the SPE column, and were lost during preconcentration. Nonetheless, positive identification of the protein was achieved, indicating the feasibility of the system for proteomics.