Liquid phase separation of proteins based on electrophoretic effects in an electrospray setup during sample introduction into a gas-phase electrophoretic mobility molecular analyzer (CE-GEMMA/CE-ES-DMA).
Bottom Line: This makes the EM determination of individual species sometimes difficult, if not impossible.This finding was consecutively applied for on-line desalting allowing EM diameter determination of analytes despite a high salt concentration within samples.Results demonstrate the proof of concept of such an approach and additionally illustrate the high potential of a future on-line coupling of a capillary electrophoresis to a GEMMA instrument.
Affiliation: Institute of Chemical Technologies and Analytics, Vienna University of Technology, Vienna, Austria.Show MeSH
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Mentions: Samples are introduced into the nano ES unit of the GEMMA system via a fused silica cone tipped capillary. During sample introduction the movement of the analytes can be calculated by taking four processes into account: (i) pressure is applied to the pressure chamber of the instrument (Δppsid) to feed the sample containing electrolyte solution continuously to the nano ES capillary; (ii) upon application of electrolyte solutions in the basic pH range, electroosmosis occurs – the EOF (vEOF = E × μEOF) is directed to the cathode of the instrument, i.e., to the capillary tip (nano ES process operated with positive high voltage); (iii) the analytes electrophoretic net mobility μieff has to be regarded as well; (iv) finally, a mixed sheath flow of CO2 and air is applied at the capillary tip in order to transport droplets of the nano ES process to the nano DMA which may have a small impact (Δpsheath) on the pressure difference along the capillary. Fig. 1 gives an overview on respective contributions to analyte migration. Assessment of individual velocity contributions allows calculation of the overall time needed for analytes to pass through the GEMMA setup. The time needed for the analyte to pass through the nano DMA and to reach the CPC unit of the instrument is neglected as it is constant for all presented experiments. In doing so, the influence of Δppsid and Δpsheath on migration time of analytes can be calculated using Hagen–Poiseuille equation (capillary inner diameter, ID, d, 25 μm; in simplification the dynamic viscosity value of water, η, 1.002 mPa s, at 20 °C is used; length of capillary, L, 26 cm). The total movement of the analyte can be calculated with the following equation:(1)v=2d×(Δppsid+Δpsheath)32×η×L+E×(μEOF−μieff)
Affiliation: Institute of Chemical Technologies and Analytics, Vienna University of Technology, Vienna, Austria.