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. First surface of the graphene was modified with acid mixtures, potassium persulfate (KPS) in an alkaline media, tetra hydro furan (THF), Octadecyl amine and sodium dodecyl benzene sulfonate (SDBS) as synthesis. By procedure, the chromium ions was extracted from water/wastewater sample 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 waters. 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 electrothermal atomic absorption spectrometry (ET-AAS). The results showed, the sulfonated and amine graphene can successfully extracted 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, limit of detection and preconcentration factor were obtained 0.02–2.4 µg L−1, 5.0 ng L−1 and 20.2 for 10 mL of water samples, respectively for Cr(III,VI) (%RSD<5%, pH=4). The validation of methodology for speciation of chromium was confirmed by spiking real samples.