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Precise small volume sample handling for capillary electrophoresis

Mozafari, Mona, Nachbar, Markus, El Deeb, Sami
Electrophoresis 2015 v.36 no.21-22 pp. 2665-2669
beta-lactoglobulin, capillary electrophoresis, coagulation, enoxaparin, ligands, myoglobin, oils, ovalbumin, silicone, sodium
CE is one of the most important analytical techniques. Although the injected sample volume in CE is only in the nanoliter range, most commercial CE instruments need approximately 50 μL of the sample in the injection vial to perform the analysis. Hence, in order to fully profit from the low injection volumes, smaller vial volumes are required. Thus experiments were performed using silicone oil, which has higher density than water (1.09 g/mL) to replace sample dead volume in the vial. The results were compared to those performed without using the silicone oil in the sample vial. As an example five standard proteins namely beta‐lactoglobulin, BSA, HSA, myoglobin, and ovalbumin, and one of the coagulation cascade involved proteins called vitonectin were investigated using CE. Mobility ratios and peak areas were compared. However, no significant changes were observed (RSDs% for mobility ratios and peak areas were better than 0.9 and 5.8%, respectively). Afterwards, an affinity CE method was used to investigate the interactions of two proteins, namely HSA and vitronectin, with three ligands namely enoxaparin sodium, unfractionated heparin, and pentosan polysulfate sodium. Mobility shift precision results showed that the employment of the filling has no noticeable effect on any of the protein–ligand interactions. Using a commercial PrinCE instrument and an autosampler the required sample volume is reduced down to 10 μL, and almost this complete volume can be subsequently injected during repeated experiments.