Capillary electrophoresis provides rapid separations and consumes only nanoliter volumes of sample per run. This separation technique is important to biomolecules including proteins. However, non-specific adsorption of proteins to the fused silica capillary limit the utility of the method. Several coatings have been developed to address this limitation including semi-permanent phospholipid coatings. Semi-permanent phospholipid coatings are prepared in-capillary each day and may be regenerated in between runs. An alternative to semi-permanent phospholipid coatings are polymerized phospholipid coatings which can be fabricated and permanently stored for several months. In this way, no capillary pretreatment is required prior to the electrophoresis separation. In this report phospholipids are polymerized in situ with ultraviolet irradiation to create a permanent coated capillary which can be stored and reused. The permanent phospholipid coating was characterized by measuring the electroosmotic flow using a previously reported method based on the profile of three injections of a neutral marker. Compared to an unmodified fused silica capillary which had an electroosmotic flow of 3.4 ×10⁻⁴cm²/V s, the capillary containing a polymerized phospholipid at the surface has a decreased electroosmotic flow of 2.9×10⁻⁵cm²/V s. The stability of the coating is characterized by measuring the reproducibility of the electroosmotic flow within the day and across day and has a relative standard deviation of 3% and 4%, respectively. The polymerized phospholipid coating is stable in between pH 3-7; however, the electroosmotic flow reveals a pH dependence. The utility of this capillary modified with the polymerized phospholipid coating is demonstrated with separations of the anionic alpha 1-acid glycoprotein or of cationic proteins at various pH values.

Lisa Holland

Professor of Chemistry, West Virginia University

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