Analysis of Sudan dyes in lipstick samples by cloud-point extraction and high-performance liquid chromatography

Abstract

A sensitive and simple method for high-performance liquid chromatography (HPLC) determination of Sudan dyes in lipstick samples after preconcentration by cloud point extraction (CPE) has been developed. The nonionic surfactant Triton X-114 was chosen as the extraction medium. Various experimental conditions were investigated to optimize the extraction and preconcentration process. Under optimum conditions, 3% Triton X-114 (v/v), ultrasonication for 20 min, pH 7, the satisfied recoveries of Sudan dyes were obtained. For the preconcentration of Sudan dyes by cloud point extraction, the solution was incubated in a thermostatic water bath at 60 °C for 10 min, and 22.5% sodium chloride (m/v) was added to the solution to facilitate the phase separation and increase the preconcentration factor. The limits of detection for the analytes are 0.11, 0.10, 0.07 and 0.08 μg g⁻¹, respectively. The intra-day and inter-day precisions of four Sudan dyes are in the range of 4.6–6.4% and 4.4–6.7%, respectively. The recoveries of four Sudan dyes are 89.3%, 90.3%, 91.8% and 92.0%, respectively. The results demonstrate that this method is simple, rapid, sensitive and low cost. Moreover, it does not require the large consumption of organic solvents and is a non-toxic and eco-friendly method.