Determination of rhodamine B in lipsticks by high performance liquid chromatography after extraction with AOT reversed micelles

In this study, we investigated the possibility of reverse micelles which were used for the determination of rhodamine B in lipsticks followed by high performance liquid chromatography (HPLC). The reverse micelle of surfactant sodium 1,4-bis(2-ethylhexoxy)-1,4-dioxobutane-2-sulfonate (AOT) was formed in n-hexane. First, the samples were preprocessed by reverse micelle extraction, and then rhodamine B was extracted from the mixture with methanol by back-extraction. The effects of different parameters including the concentration of surfactant, pH, amount of potassium chloride, ultrasonic time and type of organic solvents were evaluated and optimized during reverse micelle formation. The limit of detection of rhodamine B was 0.01 mu g g(-1). The intra-day and inter-day precisions expressed as relative standard deviations were 3.6% and 4.5%, respectively. The recovery of rhodamine B obtained was 95.0%. The reverse micelle method proposed for the determination of rhodamine B in real samples of lipsticks has the advantages of simplicity, speed, high precision, low detection limit and the use of inexpensive equipment.