Indirect determination of chlorine and fluorine in eye shadow by ion chromatography after an eco-friendly sample preparation method based on combustion reaction

A powerful and efficient method for indirect determination of chlorine and fluorine in eye shadow is described in this work. The presence of these elements should be controlled in eye cosmetics because of its allergenic properties. The proposed method combines the analyte volatilization from eye shadow based on combustion reaction and the indirect determination of Cl and F by ion chromatography as chloride (Cl-) and fluoride (F-). To achieve better combustion conditions as well as to improve the volatilization of Cl and F from the sample matrix (which is mostly inorganic), microcrystalline cellulose was evaluated as a volatilization aid. The central composite rotatable design was used to optimize the sample mass and volatilization aid mass to be used in the microwave-induced combustion. Afterward, water or ammonium carbonate solutions (50, 100 or 150 mmol L-1) were evaluated for Cl and F absorption. Using the selected conditions (200 mg of eye shadow, 400 mg of microcrystalline cellulose, and water as absorbing solution) recoveries for Cl and F were 100 +/- 8% and 106 +/- 7%, respectively. Moreover, a mixture containing the certified reference material MESS-4 (marine sediment), microcrystalline cellulose and the sample was prepared by microwave-induced combustion, and no significant difference was observed between the result obtained for Cl (11,269 +/- 325 mg kg(-1)) and the certified value (13,100 +/- 4400 mg kg(-1)). The proposed method showed suitable trueness, precision (the repeatability and the intermediate precision was always lower than 7%) and limits of detection (LODs) for Cl (60 mg kg(-1)) and F (20 mg kg(-1)). Extraction of Cl and F from eye shadow assisted by ultrasound was also evaluated; however, the Cl and F recoveries were not quantitative and the LODs were considerably high. To the best of our knowledge, this is the first work demonstrating a reliable method for multielement determination in eye shadow, which is safe, presents low generation of laboratory effluents and may be considered an efficient approach for routine analysis in cosmetic industry.