Quantitative and qualitative precision improvements by effective mobility-scale data transformation in capillary electrophoresis analysis

Abstract

By transforming the time-based x-axis of electropherograms in capillary zone electrophoresis (CZE) into the corresponding effective mobility-scale, we propose a simple and robust data representation for a better qualitative and quantitative capillary electrophoresis (CE) analysis. The time scale of the raw electrophoretic data (detection signal versus time) is transformed into an effective electrophoretic mobility scale (mu eff-scale) with account of the electroosmotic flow (EOF) peak or of an internal standard of known effective mobility. With the new scaling (detection signals versus effective mobility), the obtained electropherograms are more representative of the velocity-based electrophoretic separation and the comparison of complete electropherograms is directly possible. This is of importance when tracking peaks in real samples where alteration in EOF stability can occur or when comparing electrophoretic runs from different experimental setups (independence in column length and voltage). Beside the qualitative possibilities, a quantitative improvement is achieved in the mu eff-scale with significant better peak area reproducibility and equal to more precision in quantitative analysis than with the primary time-scale integration.

Reproducible chiral capillary electrophoresis of methamphetamine and its related compounds using a chemically modified capillary having diol groups

“…In particular, chemical variations on the inner surface can affect the EOF and hence the analyte migration times. SchmittKopplin et al [18] reported that the low reproducibility in migration time was often caused by small changes in the EOF due to uncontrollable alterations of the capillary surface, leading to unpredictable migration time shifts, especially when analyzing actual samples (matrix effects). The adsorption of urine matrices to the inner wall, which may change the surface conditions and vary the EOF, seems to be prevented by the diol moiety.…”

Capillary electrophoresis – mass spectrometry: 15 years of developments and applications

“…When coupling CE to MS, these major differences need to be fully understood and controlled to optimize the system the best (in terms of reproducibility, sensitivity, selectivity). The dissimilarities are not only due to the fact that the separations are based on relative electrophoretic velocities; this phenomenon per se leads to specific ways to qualitatively (and quantitatively) interpret electropherograms (mobility scale transformation [3,4]). Additionally, two essential processes are responsible for possible variability and need to be kept in mind when switching from chromatography to CE: (i) When injected hydrodynamically, the sample volumes are directly dependent on the viscosity and the type of separation capillary; these parameters thus directly influence the local concentration of sample at the detector (and may cause an under-or overloading).…”

Profiling preparations of recombinant birch pollen allergen Bet v 1a with capillary zone electrophoresis in pentamine modified fused-silica capillaries

“…Altogether, this entails variability not only in the EOF but also for the t m of the analytes. Therefore, identification of proteins should ideally be based on their µ eff , since this parameter is a unique property of the analyte as long as experimental conditions are well defined [70,71] and will not be affected by EOF fluctuations [71,72]. Although the suitability of this approach has been demonstrated for small molecules, the situation is less straightforward for proteins.…”