Protein adsorption onto capillary wall often hampers CE separations, particularly in the CZE mode. Electrostatic interactions are not the only factors affecting adsorption, as hydrophobic interactions and/or protein conformational changes are also involved in the adsorption phenomenon. Numerous methods can be used to reduce or avoid adsorption, such as (i) addition of low molecular weight molecules in the BGE, (ii) use of surfactants, or (iii) capillary coatings. However, most of these methods are not MS-compatible. In this study, we evaluated the addition of organic solvent as an alternative MS-compatible method to decrease protein adsorption. The effect of the solvent addition was emphasized using classical methods for estimating reversible and irreversible adsorption. In many cases, organic solvents were effective at decreasing adsorption. However, the influence of the organic solvent on protein adsorption should be evaluated case-by-case in CE method development.

Inverse Gas Chromatography (IGC) is used to study the influence of relative humidity and chemical treatment with sulfochromic acid on the surface properties of glass beads. The humidity of the carrier gas to the chromatograph is controlled by means of a specially designed humidity generator to allow investigation of the surface of powders attributed to the progressive coverage by water molecules. The solid under test is glass beads with a very a low specific surface and the properties studied are the specific surface, thermodynamic parameters and the proportions of silanol and siloxane groups on the surface.