Comparison of the electrophoretic separation of proteins in capillaries with different inner diameter

Characterization of linearly coupled capillaries with various inner diameters in the context of capillary electrophoresis

As a result of continuous instrumental progress, capillary electrophoresis has become an established separation technique. However, the choice of the suitable capillary inner diameter is sometimes difficult due to different instrumental requirements concerning injection, separation, or detection. To overcome this problem, we assembled two capillaries with different inner diameters, meaning that the inner diameter of the capillary at the injection side was different from that at the detection side. Since this was a rather uncommon approach, we focused on the associated effects in this proof-of-concept study. For the experiments, a non-aqueous model system was used, consisting of an acetonitrile-based background electrolyte and the two ferrocene derivates, ferrocenemethanol and decamethylferrocene. Using capillary flow injection analysis hyphenated to capacitively coupled contactless conductivity detection, it could be shown that fragmented capillaries of the same inner diameter had slightly lower volume flow rates than non-fragmented capillaries. With non-aqueous capillary electrophoresis hyphenated to UV detection, it was found that the coupling of capillaries with different inner diameter had a much stronger effect on the capillary electrophoresis flow than combinations with the same inner diameter. Additionally, if the inner diameter of the second capillary was larger than the inner diameter of the first capillary, a higher theoretical plate number and an increased sensitivity were found. Furthermore, it was found that there was no significant peak tailing introduced by the coupling.

Graphic abstract

Characterization of IgG glycosylation in rheumatoid arthritis patients by MALDI-TOF-MSn and capillary electrophoresis

An analytical method based on the combination of multistage mass spectrometry (MSⁿ) and capillary electrophoresis (CE) was developed for the analysis of immunoglobulin G (IgG) glycosylation in rheumatoid arthritis (RA) patients. It has been recently suggested that IgG glycosylation defect may be involved in RA immunopathogenesis. Complete characterization of glycans, including both qualitative and quantitative analysis, requires a combination of different techniques, and accurate, robust, sensitive, and high-throughput methodologies are important for analysis of clinical samples. In the present study, N-glycosylation of IgG in RA patients and in healthy people was characterized through identification of the released glycans using multistage matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MSⁿ), and quantitation by CE. Assignment of the IgG N-glycan structures was made through branching pattern analysis by MSⁿ with high-throughput. Further accurate quantitation indicated that galactosylation and sialylation of IgG N-glycans in RA cases were significantly lower than in healthy subjects. The results indicate that CE coupled with MSⁿ can identify abnormal glycosylation of IgG in RA patients compared with healthy people, and that the present work is useful for RA mechanism studies and RA diagnosis. Graphical Abstract Qualitative and quantitative analysis of IgG glycosylation in rheumatoid arthritis patients by MALDI-TOF-MSⁿ and capillary electrophoresis.