World Journal of
Pharmaceutical and Life Sciences

ENHANCEMENT OF COATING STABILITY FOR CAPILLARY ZONE ELECTROPHORESIS OF PROTEINS IN DDAB MODIFIED SURFACES

Anisa Elhamili*, Douglas Westerlund, Jonas Bergquist and Stellan Hjertén

ABSTRACT

Separation of basic proteins with capillary electrophoresis was performed using a cationic double chain N, N-didodecyl-N, N-dimethylammonium bromide (DDAB) as coating reagent for fused silica capillaries and ammonium acetate as background electrolyte (BGE) at pH 4.0, 70 mM. This double-chained surfactant forms a semi-stable coating that provides a strong electro-osmosis flow (EOF) toward the anode. To maintain the highest efficiency and reproducibility, such coating must regularly be regenerated. The temporal stability of the coating was improved by a new procedure which increases the hydrophobic interaction between the DDAB coating and the silica wall and thus makes the coating more stable and at the same time the electrostatically adsorbed proteins are released. The procedure includes rinsing the capillaries, which were kept overnight in 1.0 mM DDAB solution, with (1:1 v/v) 0.5 M NaCl in the BGE. Rinsing the capillaries with this solution gave a stable coating which permitted the separation of proteins for up to 3 consecutive days without recoating and with maintained good precision in migration times of the analytes and EOF measurements compared to the previously published method in which the capillary can be used for 9 hours only.

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