Extraction and Quantification of Hexavalent Chromium inEyeshadow Toy Cosmetics Using Ultrasonic Nebulization MassSpectrometry and Anion Exchange Chromatography: Strategiesto Prevent Chromium Species Interconversion

Abstract

Hexavalent chromium is a potent carcinogen occasionally detected in cosmetics as a trace impurity originating from raw materials or manufacturing processes. Its presence in children’s toy eyeshadows poses serious health concerns due to potential dermal or mucosal absorption. Accurate Cr (VI) quantification is hampered by interconversion with Cr (III), especially during extraction and chromatographic analysis. This study presents a robust and sensitive analytical method for selective Cr (VI) determination in complex cosmetic matrices using ion chromatography coupled with inductively coupled plasma mass spectrometry, enhanced by ultrasonic nebulization. An optimized extraction protocol was developed employing a weakly alkaline buffer containing 2 mM tetrabutylammonium hydroxide to stabilize Cr (VI) and prevent reduction. The final method achieved a limit of detection of 0.3 µg/L and limit of quantification of 0.9 µg/L. Recovery experiments demonstrated that more than 99% of Cr (VI) could be efficiently extracted after two mild extraction cycles, whereas Cr (III) exhibited poor recoverability, even when subjected to harsh extraction conditions. Consequently, Cr (III) was quantified by subtracting Cr (VI) from total chromium, determined after microwave-assisted digestion. Method validation using in-house prepared reference materials confirmed satisfactory trueness (11-15%) and precision (CV ≤ 7.9%). Application to seven commercial toy eyeshadows revealed Cr (VI) levels below the regulatory limit (1.0 mg/kg), although total chromium concentrations indicated the prevalent presence of Cr (III). This methodology provides a
reliable and regulatory-compliant approach for Cr (VI) speciation in cosmetic products, supporting consumer safety, particularly in paediatric populations.