Development of analytical method for determination of 1,4-dioxane in cleansing products.

OBJECTIVE: 1,4-Dioxane is a toxic by-product formed during the synthesis of surfactants used in finished cosmetic products. There are no set permissible levels of toxic impurities in finished cosmetic products in Japan. In this study, we have established a simple and sufficiently precise analytical method to determine the activity of 1,4-dioxane in finished cosmetic cleansing products. METHODS: This method involves the standard addition approach and headspace-gas chromatography/mass spectrometry without pre-conditioning. RESULTS: Fifteen cleansing products that are sold in the Japanese market, such as shampoo, hand soap, and dishwashing liquid, were analyzed, and 1,4-dioxane was detected at a concentration of a few micrograms per gram of the product in almost all of them. The concentration of 1,4-dioxane in two dishwashing liquid products was high. The maximum concentration of 1,4-dioxane in all of the cleansing products was below 10 µg g(-1) , which is a limit that is thought to be safe and technically achievable through the application of good manufacturing practices. Since 1,4-dioxane is formed during the synthesis of polyoxyethylene ether sulfate, it was detected at high concentrations in cleansing products that contained a lot of polyoxyethylene ether sulfate. CONCLUSION: Control of the synthesis of polyoxyethylene ether sulfate can be effective in reducing the concentration of 1,4-dioxane in cleansing products.