Abstract
The voltammetric behavior of two acidic catecholamine metabolites, vanillylmandelic acid (VMA) and homovanillic acid (HVA) in the presence of cationic, anionic, or nonionic surfactants was monitored at the disposable screen-printed electrodes. In basic medium above their pKa values, the cationic surfactant cetylpyridinium chloride (CPC) enhanced the oxidation peak current based on electrostatic and hydrophobic interactions with the ionized carboxylic group and stabilization of some of the electrochemical reaction intermediates. Under the optimum measuring conditions at pH 9.5, calibration graphs were linear within HVA concentration range from 0.25 to 2.5 x 10(-6) mol l(-1) and LOD 0.021 x 10(-6) mol l(-1). Simultaneous assay of HVA in the presence of VMA within the submicromolar concentration range can be performed with acceptable average recovery of 106.0 +/- 3.4%. This preliminary study represents the base for simultaneous quantification of both compounds in of urine samples for Neuroblastoma diagnosis.