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: Initial CE experiments were carried out at pH 7.4, 8.4, and 9.4, respectively. However, stable electrophoresis conditions were found only at slightly basic pH values; therefore, pH 9.4 was further applied for the GEMMA experiments. For this pH value, the time needed for BSA and IgG to migrate across the capillary considering Δppsid, μEOF, μieff was calculated as detailed above. The estimated time to pass the capillary was about 370 s for IgG and about 400 s for BSA (Δp = 1 psid, E = 3.1 kV m−1). The difference of migration times can be explained by different mobilities of respective proteins upon electrophoresis. Fig. 3 depicts corresponding spectra obtained in FM. The different time needed to pass a capillary for BSA (black) and IgG (grey) is clearly demonstrated. The migration time of IgG is about 30 s less than the migration time of BSA confirming theoretical calculations. However, it must be noted that the theoretically estimated migration times of analytes were approximately 80 s higher than measured values. A possible explanation for this observation might be found in uncertainties of the inner diameter of the used capillaries as well as in the pressure gauge of the instrument which is not designed for pressure determination with high precision. Differences between calculated and observed migration times can result from actual pressure values slightly deviating from read out values given by the instrument.
Affiliation: Institute of Chemical Technologies and Analytics, Vienna University of Technology, Vienna, Austria.