Determination of glucosamine content in nutraceuticals by capillary electrophoresis using in-capillary OPA labeling techniques

Capillary electrophoresis (CE) procedure was developed for determining glucosamine content in nutraceuticals. Glucosamine was labeled with o-phthalaldehyde (OPA) by mixing with the OPA reagent (4.5 mM OPA, 4.5 mM 2-mercaptoethanol dissolved in 20 mM borate buffer, pH 9.3). The fluorescent OPA-glucosamine adduct was separated and detected at A340 within 3 min. The pre-capillary labeling reaction can be performed by sequentially injecting OPA/sample/OPA segments into the separation capillary; the in-capillary labeling technique simplified the sample pretreatment and improved its reproducibility. The linear dynamic range of the in-capillary labeling CE method was 0.1~30 mM. No sample pretreatment procedure was required for tablets containing mainly starch or other sugar as the vehicles.