Modification of graphene for speciation of chromium in wastewater samples by suspension solid phase microextraction procedure

       In this study, the surface modification of graphene (SMG) was developed for efficient speciation and determination of chromium in water and wastewater samples. By procedure, the chromium ions were extracted from water/wastewater samples based on sulfonated and amine graphene (S-NG, N-NG) by suspension solid-phase microextraction procedure (SMSPE). Hydrophobic ionic liquid ([HMIM] [PF6]) was used for separation graphene from 10 mL of water. After shaking and centrifuging, the phase of Cr→ S-NG, Cr→N-NG was back-extracted by 0.2 mL of HNO3 (0.4 mol L-1) and finally chromium concentration determined with ET-AAS. The results showed the sulfonated and amine graphene can successfully extract Cr(III) and  Cr(VI) from water and wastewater samples at pH=3.5-5.5 and pH<3, respectively. Also, the most Cr(VI) extracted by N-graphene at pH=2(NH3+→Cr2O7─). Under the optimal conditions, the linear range, LOD, and preconcentration factor were obtained 0.02–2.4 µg L−1, 5.0 ng L−1 and 20.2, respectively for Cr(III, VI) (%RSD<5%).