Development of a simple capillary electrophoretic determination of glucosamine in nutritional supplements using in-capillary derivatisation with o-phthalaldehyde

Abstract

A simple capillary electrophoretic method was developed for the determination of glucosamine using in-capillary derivatisation. Glucosamine in commercial products was extracted with purified water. The CE separation was achieved on an uncoated fused-silica capillary using a 20mM borate buffer (pH 9.2) containing 5mM o-phthalaldehyde (OPA) and 5mM 3-mercaptopropionic acid (MPA) at 25kV, followed by UV detection at 340nm. The detector response was linear (r2>0.999) in the concentration range 10–1000μg/mL. The limit of detection (LOD) was 1.3mg/g. Spiked glucosamine recoveries at 50 and 100mg/g level were 95.1% and 104.3%, respectively. The method was applied to 16 commercial products. The concentrations of glucosamine were 109–705mg/g, and the ratios of detected glucosamine content to the labelled value were 88.8–124%. No significant bias was observed (r2=0.989, p<0.01), between results obtained by the proposed CE method and an official colorimetric method (Japanese Health Food & Nutrition Food Association).