Synthesis of Quaternary Ammonium Derivatives of Cellulose as the Coating Reagents for Capillary Electrophoresis

Abstract

In this work, quaternary ammonium group-modified celluloses (QCs) were homogeneously synthesized by reacting cellulose with 3-chloro-2-hydroxypropyltrimethylammonium chloride in NaOH/urea solutions. The structure and solution properties of the QCs were characterized by elemental analysis, FT/IR, ¹H-NMR, and size exclusion chromatography. The results show that water-soluble QCs, with degree of substitution values, defined as the substitution of free hydroxyl groups of cellulose, 0.49–0.72 and molecular weight 21–66 kDa could be obtained by optimizing the reaction time. The synthesized QCs were tested for protein separation as physically adsorbed coatings in capillary electrophoresis. Among the derivatives studied, quaternary ammonium cellulose showed rapid electroosmotic mobility and effective suppression of protein adsorption. The EOF can be manipulated for various applications by using QCs with different molecular weight. Because the reversed EOF can be obtained over a broad pH range, it is possible to separate basic, neutral, and acidic proteins under physiological conditions. Eight proteins; lysozyme, ribonuclease A, cytochrome C, α-chymotrypsinogen, α-lactalbumin, ovalbumin, transferrin, and myoglobin were baseline separated within 25 min by 25 mM sodium phosphate buffers (pH 7.0) containing 100 µg/mL QC.