Electrochemical determination of chemical oxygen demand on functionalized pseudo-graphite electrode

Graphite-like carbon electrodes produced from the University of Idaho thermolyzed asphalt reaction (GUITAR) were examined for anodic sensing of chemical oxygen demand (COD). For maximum sensitivity the surfaces were modified with quinone functionality (q-GUITAR). Analysis by FT-IR indicated C-OH and C=O groups on the surface which was verified by and X-ray photoelectron spectroscopies (XPS). The capacitance as measured by cyclic voltammetry (CV) of q-GUITAR is 170 times greater in 1.0 M H2SO4 than the pristine material indicating a more hydrophilic surface. This enhances the anodic oxidations of the COD surrogates consisting of glucose, potassium hydrogen phthalate (KHP), lactic acid, and sodium dodecyl benzenesulfonate (SDBS). At a constant potential of 1.6 V vs. Ag/AgCl q-GUITAR anodes have the largest linear range of 0 to 10,000 ppm (as glucose) reported in literature. The limit of detection (40 ppm) and sensitivity are competitive with other electrode systems.