On-Line Solid-Phase Extraction Capillary Electrophoresis Mass Spectrometry for Preconcentration and Clean-Up of Peptides and Proteins

Abstract

One of the major drawbacks of capillary electrophoresis (CE) and other microscale separation techniques, for the analysis of low abundant peptides and proteins in complex samples, are the poor concentration limits of detection. Several strategies have been developed to improve CE sensitivity. Here, we describe an on-line solid-phase extraction capillary electrophoresis mass spectrometry method with a commercial C18 sorbent for clean-up and preconcentration of neuropeptides from highly diluted biological samples.

A critical retrospective and prospective review of designs and materials in in-line solid-phase extraction capillary electrophoresis

“…Over the years, different strategies have been described to decrease the limits of detection in capillary electrophoresis (CE) [1][2][3][4][5][6]. High selective and sensitive detectors (e.g mass spectrometry (MS) and fluorescence detectors [7,8]) or the traditional off-line sample clean-up and preconcentration techniques have been widely applied [9][10][11][12].…”

“…High selective and sensitive detectors (e.g mass spectrometry (MS) and fluorescence detectors [7,8]) or the traditional off-line sample clean-up and preconcentration techniques have been widely applied [9][10][11][12]. At the same time have been developed the on-line electrophoretic [1][2][3][13][14][15] and chromatographic approaches to minimize sample handling and increase analysis throughput [4][5][6].…”

“…However, the dependence of these techniques on the analyte and sample matrix physicochemical properties, especially the electrical charge, hinders their performance in many applications. Chromatographic preconcentration techniques, which can be broadly categorized as on-line solid-phase extraction capillary electrophoresis (SPE-CE), show a more general applicability and can be also very efficient yielding high preconcentration factors (typically between 100 and 10,000 times) [4][5][6][16][17][18][19][20][21]. In on-line SPE-CE, a microcartridge (or analyte concentrator) is inserted near the inlet of the separation capillary.…”

“…The term in-line SPE-CE has been preferred in the last years by many authors because is more specific, as it allows differentiation from on-line devices using valves or more complex instrumental set-ups. In in-line SPE-CE the microcartridge is integrated in the separation capillary, the voltage is applied across to it and the system is operated without valves [4,5,[17][18][19][20][21]. In either case, the microcartridge contains a sorbent to selectively retain the target analyte, hence enabling the hydrodynamic or electrokinetic introduction of a large volume of sample (∼50-100 μL).…”

“…After sample loading, the capillary is rinsed to eliminate non-retained molecules and filled with background electrolyte (BGE). Then, the analyte is eluted in a small volume of an appropriate solution (~25-50 nL), resulting in sample clean-up and concentration enhancement before the electrophoretic separation and detection [4]. The higher the loaded volume while the analyte is retained without exceeding the breakthrough volume, the higher the preconcentration factors are obtained for a certain elution volume [21].…”