GREEN SYNTHESIS OF MAGNETIC REDUCED GRAPHENE OXIDE FOR MAGNETIC SOLID PHASE EXTRACTION OF SYNTHETIC COLORANTS IN BEVERAGES AND FOODSTUFFS PRIOR TO SPECTROPHOTOMETRIC ANALYSIS

Abstract

Adulteration of foodstuffs and beverages with harmful synthestic food colorants are a global concern, but lacks uniform legislation. Colored foods, confectionarries, and beverages that may contain harmful synthetic dyes are widely marketed in Ethiopia. This study aims to develop a green and rapid method to determine the concentration of synthetic food dyes in colored foods, confectioneries, and beverages. To this end, magnetized reduced graphene oxide nanocomposite was green synthesized using unchewable Khat leaf extract. The synthesis of graphene oxide (GO) and the reduction of GO as well as the magnetization of rGO was characterized by UV-Vis spectrophotometer, FT-IR, XRD, SEM-EDS, and changes in colors were visually inspected. The synthesized Fe3O4/rGO NCs was used as adsorbent for development of magnetic solidphase extraction (MSPE) for extraction of synthetic dyes in foodstuffs and beverages. The effect of different factors on extraction efficiency such as pH (4), adsorbent dose (0.05 g), contact time (30 min), sample solution volume (10 mL), agitation speed (30 min), and the initial dye concentration (5 mg/L) were investigated and optimized. The method was validated in wide linear range of 0.1-75 mg/L and with LOD of 1.31, 1.78, 1.34, and 4.58 mg/L and LOQ of 4.36, 5.9, 4.46, and 15.28 mg/L for ponceau4R, Sunset yellow FCF, tartrazine, and sudan III, respectively. The repeatability and reproducility of the method (intra- day, n=6 and inter-day for six days, n=6) were examined revealing high precision (%RSD) of 0.092%-0.604% and 0.098%-0.837%, with recovery (%) in the range of 85.3% to 97.3% and 85.3% to 97.1%, respectively, which is in acceptable range. Finally, the developed MSPE was applied to real samples (i.e. beverages, drink powders, lollipop candies, tomato pastes, and chilli powder extracts) at optimum conditions. The method is highly efficient, magnetically separable, and reusable for dye removal from beverages, drink powders, candies, tomato pastes, and chilli powder