Electrochemical impedance sensor based on nano-cobalt-oxide-modified graphenic electrode for total phosphorus determinations in water

In this work, an electrochemical sensor equipped with nano-cobalt-oxide-modified graphenic working electrode is demonstrated for the quantification of total phosphorus through electrochemical impedance spectroscopy (EIS) in water environment. Prior to EIS measurements, phosphorus with various valent ions was electrochemically oxidized to orthophosphate through anodic polarization with graphenic electrode. Orthophosphate specifically binds with nano-cobalt oxide-decorated working electrode, and the generation of Co-3(PO4)(2) on the modified electrode surface increased the electron transfer resistance, which was characterized by means of EIS. We systematically investigated the impacts of pH, ionic strength, and digestion time on analytical efficiency. Under optimal conditions, a calibration curve is obtained in the linear range of 0.013 to 1.2 mg L-1 with a detection limit (LOD) of 0.013 mg L-1, accompanied by high sensitivity and accuracy exceeding 90% in comparison with National Standard Method, and this proposed method is also well suited for the phosphorus detection in real water sample. Therefore, this designed sensor demonstrated the potential applicability to determine the phosphorus in water environment rather than traditional methods.