Determination of three Tumor Biomarkers (Homovanillic Acid,Vanillylmandelic Acid,and 5‐Hydroxyindole‐3‐Acetic Acid) Using Flow Injection Analysis with Amperometric Detection

Flow injection analysis with amperometric detection (FIA‐AD) at screen‐printed carbon electrodes (SPCEs) in optimum medium of Britton‐Robinson buffer (0.04 mol ? L^?1, pH 2.0) was used for the determination of three tumor biomarkers (homovanillic acid (HVA), vanillylmandelic acid (VMA), and 5‐hydroxyindole‐3‐acetic acid (5‐HIAA)). Dependences of the peak current on the concentration of biomarkers were linear in the whole tested concentration range from 0.05 to 100 μmol ? L^?1, with limits of detection (LODs) of 0.065 μmol ? L^?1 for HVA, 0.053 μmol ? L^?1 for VMA, and 0.033 μmol ? L^?1 for 5‐HIAA (calculated from peak heights), and 0.024 μmol ? L^?1 for HVA, 0.020 μmol ? L^?1 for VMA, and 0.012 μmol ? L^?1 for 5‐HIAA (calculated from peak areas), respectively.