A Simple and Novel Technique for the Determination of Rhodamine B in Cosmetics Based on Dispersive Surfactant Micelle-mediated Extraction and Image Colorimetric Analysis

Aims: The primary objective of this study was to develop a simple, selective, sensitive, and rapid method for the determination of trace levels of Rhodamine B in different cosmetic items. Background: At present, synthetic dyes in various colors are essential in cosmetic products, not only for adding pleasant scents, but also for enhancing their appeal and restoring natural colors. Rhodamine B, a pink synthetic azo dye, is widely used in the cosmetic industry. It poses risks if ingested by humans and animals, causing skin, eye, and respiratory irritation. Scientific studies have shown that it has carcinogenic, reproductive, developmental, neurotoxic, and chronic toxic effects on both humans and animals. Therefore, the improvement of precise and fast measurement techniques for detecting Rhodamine B in different sample types is crucial. Objective: The objective of this study was to find a fast, accurate, and sensitive method for the determination of trace levels of Rhodamine B in different cosmetic items. Methods: The technique used has been based on Dispersive Surfactant Micelle-mediated Extraction (DSME) combined with digital image analysis. Results: The optimized method yielded a linear calibration graph ranging from 25 to 300 μg L-1, with a correlation coefficient of 0.9975 and the Limit of Detection (LOD) of 6.7 μg L-1. The proposed method was used to measure Rhodamine B in lipstick and nail polish samples, resulting in satisfactory recoveries ranging from 97.8 to 107.2%. Conclusion: DSME could remove the necessity of high temperature, hazardous organic solvents, and anionic surfactants in Cloud Point Extraction (CPE) and Catanionic Surfactants-based Coacervation Extraction (CSCE). Additionally, experiments have shown the results from digital image analysis to be in line with those from a commercial UV-Vis spectrophotometer and a spectrofluorometer. The authors believe that utilizing DSME image analysis could be a beneficial alternative to the analytical analysis of other colored species in routine analysis.