Assay of xanthene dyes in lipsticks by inverse supercritical fluid extraction and HPLC

Abstract

An inverse supercritical fluid extraction (SFE) procedure has been developed for the efficient isolation of six of the most common xanthene dyes (fluorescein; 4′,5′-dibromofluorescein; 2′,4′,5′,7′-tetrabromofluorescein; 2′,4′,5′,7′-tetrabromo-4,5,6,7-tetrachlorofluorescein; 4′,5′-diiodofluorescein and 2′,4′,5′,7′-tetraiodofluorescein) from lipstick matrices. A rapid high-performance liquid chromatographic method is also presented for the separation of the six dyes on a cyanopropyl-bonded silica column eluted with acetonitrile-methanol-acetate buffer. Extraction of the lipstick with supercritical CO2 at 350 atm and 40°C for 10 min exclusively removed the matrix components, whereas the xanthene colorants remained in the extraction vessel. After treatment with CO2, the target analytes were quantitatively recovered (>96.8%) by dispersion of the sample in ethanol under sonication. The inverse SFE method was compared with conventional liquid-liquid extraction on commercial lipstick products. The two methods produced comparable recoveries. However, inverse SFE was superior in terms of precision and speed of analysis and gave cleaner extracts.