Determination of chlorhexidine in tooth pastes by high performance liquid chromatography.

Determination of chlorhexidine in tooth paste was examined by using high performance liquid chromatography (HPLC). Chlorhexidine was extracted with methanol, isopropanol and acetonitrile. The best recovery was obtained with methanol containing acetic acid and sodium dodecyl sulfonate (SDS). Two g of sample was extracted with methanol-water-acetic acid (80 : 19.5 : 0.5) containing SDS (1%) and made up to 50 ml, and 20μl of this solution was injected to HPLC. A chlorhexidine peak was separated from other component peaks in commercial tooth paste by using an ODS column, 1-dodecansulfonate (DSA) as an ion pairing agent and methanol-water-THF (830 : 160 : 10) containing 5% acetic acid as an elution solution. The amounts of chlorhexidine in each 100 g of commercial tooth paste were ranged from 5.1 mg to 19.6 mg by this method.