Adsorptive stripping voltammetry of indigo blue in a flow system

Abstract Stripping voltammetry is one of the most sensitive electrochemical techniques. In adsorptive stripping voltammetry, the species that suffer the stripping is adsorbed on the surface of the electrode spontaneously, i.e., a previous electrolysis step is not required. In this experiment, this technique is employed to quantify the enzymatic product of an enzyme-linked immunosorbent assay (ELISA). The analyte is interleukin-10 (IL-10), a cytokine involved in the regulation of immune response. The product of the ELISA is introduced in a flow injection analysis system coupled to an electrochemical cell with a carbon paste electrode. The label used in the ELISA is the enzyme alkaline phosphatase that catalyzes the hydrolysis of the 3-indoxyl phosphate to indigo. This enzymatic product, when introduced in the flow system, is adsorbed on the surface of the carbon paste electrode and then, later on, stripping voltammetry is performed. The technique employed for recording the signal is alternating current voltammetry. The analytical signal is the current due to the redissolution of the indigo adsorbed on the working electrode. This chapter includes the ELISA protocol and the procedure for IL-10 determination by the flow injection electroanalysis method. This chapter also includes indications for writing the lab report, questions for students, and additional notes for taking into account by the instructor.