Simple and efficient removal of azo dyes from water samples by dispersive solid-phase micro-extraction employing graphene oxide with high oxygen content

A technique based on dispersive solid-phase micro-extraction (DSPµE), employing graphene oxide (GO) particle with a higher oxygen content synthesised by through a modification of the Hummers method was investigated. GO particle was characterised using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Dubinin-Radushkevich, and Freundlich models. DSPµE parameters such pH effect, adsorbent amount, and contact time were optimised in the dye removal process. The proposed method was applied for the removal of three azo dyes in tap water samples: sunset yellow (SY), allure red (AR), and tartrazine (TAR). The water samples were previously analysed using large volume sample stacking capillary electrophoresis (LVSS-CE). Maximum removal capacity was achieved under the optimal conditions of pH solution (pH = 6.0), GO amount (10.0 mg), and contact time (10 minutes) with percentages at 99.0%. The precision was measured in terms of recovery (% desorption) and relative standard deviation from 95.5 to 98.0%, RSD (<10.0%). Two positive water samples for SY and TAR were completely free of azo dyes after application of the proposed method, whereas AR was not detected in any of the ten samples.