High-performance liquid chromatographic analysis of chlorhexidine in saliva after mouthrinsing

A high-performance liquid chromatographic method was developed to quantify chlorhexidine in human saliva. After addition of an internal standard and a cidic-deproteinization, saliva samples were chromatographed by the reversed -phase ion-pair system using pentanesulfonate as a counterion and the eluat es were detected by a diode array detector. Under optimal conditions, the b aseline separation of analytes was achieved within 4.5 min without interfer ence from components in saliva matrix. The method showed high selectivity t o salivary chlorhexidine, quantitative range (50.0 ng/ml-50.0 mu g/ml), rec overy (96.0-97.8%) and analytical precision (intra- and interassay CVs with in 0.41%), permitting the effective application to both saliva and aqueous solutions. Chlorhexidine was found in saliva at microgram per milliliter le vels for at least 8 h after mouthrinsing with 10 ml of an aqueous solution of chlorhexidine (0.1 or 1.0 mg/ml) for 1 min, The concentrations of saliva ry chlorhexidine were reduced by ingesting the acidic beverage and food, bu t not by ingesting the neutral beverage. The adsorption experiments in arti ficial saliva revealed that chlorhexidine was significantly adsorbed to sal iva-coated hydroxyapatite, buccal epithelial cells and mucin. The proposed method will be a useful tool to study salivary chlorhexidine after oral app lication and its retention in the oral cavity.