Media influence on the enhancement of the fluorescence of berberine hydrochloride

Berberine hydrochloride is an alkaloid with little or no fluorescence in water. In sodium dodecylsulfate solutions, the fluorescence intensity of this compound is enhanced several folds by ion-pairing with the anion of the surfactant. The enhanced fluorescence intensity reaches a maximum at a surfactant concentration of 4 . 10(-3) M and then decreases to a constant value at the critical micelle concentration and beyond. At concentrations near the maximum, a calibration sensitivity of 3.23 . 10(6)/M was obtained. In addition, a good linear dynamic range and a low limit of detection (4 . 10(-5) and 1.5 . 10(-7) M, respectively) were determined. This observation indicates that this surfactant medium could be effectively used in fluorometric trace analysis of berberine hydrochloride. It was also observed in this work that solvents of low dielectric constant tend to stabilize this compound and thereby enhance its fluorescence.