Desenvolvimento de métodos para a determinação As, Cd, Cl, Cr, F, Ni e Pb em cosméticos usados para maquiagem

Abstract

In this study, sample preparation methods were evaluated for the subsequent As, Cd, Cr, Ni and Pb determination in lipstick by inductively coupled plasma mass spectrometry, as well as for the subsequent Cl and F determination in eye pencil and eye shadow by ion chromatography. The microwave-assisted wet digestion (MW-AD) and the microwave-induced combustion (MIC) were evaluated for lipstick sample preparation. In the MW-AD, the use of complexing acids (HF and HCl) combined with HNO3 was evaluated for the digestion of shimmering, creamy and opaque lipsticks. The results indicate that complexing acids are essential for determination of As, Cr and Pb in shimmering lipsticks. Thus, by using 6 ml of concentrated HNO3 combined with only 0.5 ml of concentrated HCl, it was possible to obtain quantitative results for Cd, Cr, Ni and Pb in all lipsticks used in this study. By using these conditions, recoveries between 92 and 114% were obtained for all analytes after digestion of creamy and opaque lipsticks, as well as for Cd, Cr, Ni and Pb after digestion of shimmering lipstick. Moreover, no statistical difference was observed between the results obtained using the proposed method (HNO3/HCl) and those obtained using the reference method (HNO3/HF). The limits of detection (LODs) obtained for analytes ranged from 2.6 to 420 ng g-1 and the relative standard deviations (RSDs) were lower than 10% for As, Cr, Ni and Pb. The RSDs obtained for Cd were of up to 16%, and these were considered suitable in view to the low concentration of Cd in the analyzed lipsticks. On the other hand, when the MIC was used for lipstick digestion, quantitative results were not obtained for analytes under studied conditions. For the development of methods for determination of Cl and F in eye pencil and eye shadow, the use of the MIC and of the ultrasound-assisted extraction was evaluated for the sample preparation. The results obtained in this study indicate that ultrasound-assisted extraction was not efficient for the subsequent determination of Cl and F in the evaluated conditions. However, the MIC was suitable for sample preparation of both samples, and it enabled the use of water as the absorbing solution for analytes, providing solutions compatible with the determination by ion chromatography. The proposed methods for Cl and F determination in eye pencil and eye shadow allow the obtainment of recoveries between 93 and 106% for both analytes, RSDs lower than 9% and suitable LODs for the determination of Cl and F in these samples.