[Studies on an analytic method for detection of prohibited ingredient, strontium dichloride in cosmetics]

Strontium dichloride is one of the prohibited ingredients in cosmetics due to the Japanese Pharmaceutical Affairs Act. We established the analytical method for strontium dichloride in cosmetics by capillary electrophoresis (CE). The toothpaste was dispersed into water. After ultrasonication for 10 min, the solution was centrifuged at 3000 rpm for 10 min. The supernatant was filtrated through a membrane (0.45 microm), diluted 100-times with water, and injected into CE. The calibration curve showed linear between the concentrations of strontium dichloride (from 2 to 50 microg/ml) and the peak area of strontium ion. Detection limit of strontium dichloride is 2 microg/ml. There was no interference of the ingredients in the toothpaste.