Solid phase extraction of mercury(II) using soluble eggshell membrane protein doped with reduced graphene oxide, and its quantitation by anodic stripping voltammetry

This article describes the preparation of a nanocomposite consisting of soluble eggshell membrane protein (SEP) doped with reduced graphene oxide (rGO) as a sorbent for the preconcentration of mercury(II) by solid phase extraction (SPE). Incorporation of rGO was accomplished by dissolving the eggshell membrane in a mixture of thioglycolic acid and acetic acid, adding graphene oxide, and sonicating the solution. The brown GO-SEP nanocomposite was then chemically reduced to black rGO-SEP using hydrazine as the reducing agent. The nanocomposite was found to be an efficient nanosorbent for SPE of mercury(II). Following desorption of Hg(II) ions from the sorbent with thiourea, Hg(II) was quantified by anodic stripping voltammetry. Under optimized extraction and electroanalytical conditions, the method has a wide analytical range that is linear in the 0.5-80 ng mL(-1) Hg(II) concentration range. The lower detection limit is 0.14 mg mL(-1), the enrichment factor is 50, and the sorption capacity is as high as 77 mg g(-1).