Capillary electrophoretic bioanalysis of therapeutically active peptides with UV and mass spectrometric detection after on-capillary preconcentration

Abstract

An earlier developed capillary electrophoresis (CE) system with an on-capillary adsorptive phase is investigated for its suitability to quantitate low concentrations of angiotensin II and gonadorelin in plasma. An off-line solid-phase extraction is used for sample preparation. The on-line preconcentration CE system allows multiple capillary volumes of sample solution to be injected, increasing the concentration sensitivity of CE with 3-4 orders of magnitude. Furthermore, possible influence of matrix salts can be ruled out by employing a rinsing step after sample application. Using short-wavelength UV detection, reproducibility and linearity in the low nanomolar range were satisfactory. The capillary could be efficiently regenerated using a programmed between-run rinsing procedure, allowing 20-30 large injections of sample extracts. Coating of the capillary improved the robustness of the method. Mass spectrometric detection via a previously reported sheathless interface increased the selectivity and sensitivity substantially. Recommendations are provided for the sample preparation process, the most critical part of the system. Further purification of the sample is required to allow the loading of larger sample volumes and to optimize the system's robustness.

Sorbent preconcentration procedures coupled to capillary electrophoresis for environmental and biological applications

“…Waterwal et al [80][81][82] reported some studies regarding the use of mPC-CE for the preconcentration and separation of angiotensin II and gonadorelin. In a preliminary study they compared different in-line SPE-CE designs for preconcentrating the two peptides.…”

“…After coupling the same mPC-CE system to a mass spectrometer using a sheathless interface, the sensitivity for a standard solution of the same compounds improved considerably the picomolecular range in the selected ion monitoring mode (SIM) [81]. Finally, the authors used this approach (mPC-CE-MS) to determine the two peptides in spiked plasma samples in the low nanomolar concentration level [82] but in this case for avoiding contamination of the membrane and of the capillary wall a pre-treatment step based of an off-line procedure and a rinsing of the capillary with SDS were necessary.…”

Recent Developments in Capillary Electrophoresis–Mass Spectrometry of Proteins and Peptides

“…A means to close the CE electrical circuit for analyte separation while simultaneously providing an electrical potential to the spray tip is necessary. The common interfaces can be divided into three categories: sheath-flow 16,[18][19][20]24,27,32,37,38,40,43,47,50,[53][54][55][56]60,66 and sheathless 15,17,25,26,[28][29][30]34,36,44,45,48,49,61 and liquid-junction interfaces. [92][93][94] In the sheath-flow design, a coaxial sheath liquid, usually a hydroorganic mixture, mixes with the capillary eluent at the outlet end of the capillary.…”

“…They applied this later to quantitate low concentrations of gonadorelin and angiotensin II in a plasma. 30 Janini et al 49 assembled a miniaturized, membrane-based solid-phase extractor (mSPE) using a C18-impregnated extraction disk (Fig. 4).…”

In-capillary micro solid-phase extraction and capillary electrophoresis separation of heterocyclic aromatic amines with nanospray mass spectrometric detection

“…We have chosen on-line coupling of in-capillary µSPE for sample purification and concentration, CE for separation and nESI-MS for detection. On-line SPE-CE has been reported (for analytes other than HAs) using different SPE matrices, such as packed particle beds [20,21,22,23], C 18 -impregnated membranes [24] and polymer membranes [25,26]. The focus of this work was on the construction of the µSPE-CE-nESI capillary and its use in rapid analyses of small amounts of HAs.…”