Determination of 5-hydroxy indole acetic acid at poly (paminobenzene sulfonic acid) electrode

In this study, the quantitative amount of 5-hydroxy indole acetic acid (5-HIAA) was determined by using the electrochemical oxidation property at poly (p-aminobenzene sulfonic acid) (p-ABSA) modified glassy carbon electrode. The redox property of 5-HIAA was investigated by cyclic voltammetry and differential pulse voltammetry to optimize the analytical parameters. Phosphate buffer solution at pH 7.00, in which a sharp peak and maximum current were observed at the modified glassy carbon electrode, was chosen as the supporting electrolyte for 5-HIAA. The effect of pH on the peak current and peak potential was determined by the differential pulse voltammetry technique, and the effect of scan rate on the peak current was determined by the cyclic voltammetry technique. The cyclic voltammograms showed that the redox reaction of 5-HIAA was irreversible. Scan rate study with cyclic voltammetry showed that the redox reaction of 5-HIAA was controlled by both diffusion and adsorption on the poly (p-ABSA) modified glassy carbon electrode. Differential pulse voltammetry technique was used for the quantitative analysis of 5-HIAA. The linear working range of the obtained calibration graphs was determined as 1×10-5 – 9×10-5 M (correlation coefficient 0.9912), and the detection limit was determined as 5.3x10-7 M. Recovery values in the analysis of urine samples were between 99.4% and 103.0%. The results showed that the modified electrode can be applied to the determination of 5-HIAA in the presence of ascorbic acid. The proposed sensor is promising for routine analysis due to its high selectivity, reproducibility, long-term stability, and high recovery values obtained in biological samples.