Solid phase microextraction of rhodamine B in cosmetic samples using ZnS@GO@WMCNTs Nanocomposite with Spectrophotometric Detection

Abstract

Rhodamine B dye (RhB) has carcinogenicity, genotoxicity, neurotoxicity and toxicity on living cells and therefore its use is prohibited. but it is still secretly used in cosmetics and foods. For this reason, it is important to develop analytical methods for accurate and sensitive analysis of trace levels of RhB dye in cosmetic and food samples. In this study, a new solid phase microextraction method (SPME) was developed for quick and cheap analysis of RhB in cosmetic samples. A new nanohybrid material including graphene oxide (GO), multi-walled carbon nanotubes (MWCNTs) and zinc sulfide nanopartices (ZnS) was synthesized by hydrothermal synthesis method and the new ZnS@GO@WMCNTs nanohybrid material was used as sorbent in simultaneous separation and preconcentration of RhB from cosmetic products by SPME. ZnS@GO@WMCNTs material was characterized by Raman spectroscopy, scanning electron microscopy (SEM), SEM-Mapping and energy dispersive X-Ray fluorescence (EDX) techniques. The effects of experimental parameters such as amount of sorbent, pH of sample solution, sample volume, effects of matrix, eluent solutions on the recoveries of RhB were investigated. RhB dye adsorbed on ZnS@GO@WMCNTs was eluted with acetic acid–ethanol mixture (2:1) and determined by using UV–Visible spectrophotometer at 550 nm. The fact that RhB adsorbed quantitatively on the adsorbent at all pH values shows that strong Van der Waals interactions between the ZnS@GO@WMCNTs and RhB molecules are effective in adsorption. In optimal experimental conditions, the limit of detection (LOD) and preconcentration factor (PF) of the proposed MSPE-UV/Vis spectroscopy procedure were 4.74 and 44, respectively. The MSPE-UV/Vis procedure was successfully applied to the microextraction and determination of RhB in nail polishs ve lipstick samples with recoveries in the range 95–101 %.