Electrochemical Determination Of Dopamine And Uric Acid In Blood Serum Using Anionic Surfactants At Carbon Paste Electrodes

Abstract

A selective and sensitive method was developed for the simultaneous electrochemical determination of dopamine and uric acid by using a sodium dodecylbenzenesulfonate (SDBS) and sodium dodecyl sulfate (SDS) as a surface modifier of carbon paste electrodes (CPEs). At lower concentration of SDS and SDBS they form a negatively charged monolayer on CPE surface because of surfactants’ hydrophobic chain interaction with paraffin of CPE. Optimized concentration of surfactants was 2 mM for SDS and 1 mM for SDBS in phosphate buffer solution (0.1 M, pH 7 and pH 6, respectively). Compared with plain CPE, CPE modified with SDS (CPE-SDS) and CPE modified with SDBS (CPE-SDBS) have shown the improved electrochemical response of dopamine (DA) at 0.230 V and uric acid (UA) at 0.345 V due to electrostatic interactions between positively charged analytes and surface negatively charged of SDBS and SDS. Under optimal experimental conditions, the designed electrodes exhibited a wide range of linear response to DA from 0.53 μM to 31.6 μM and UA from 5.95 μM to 118.97 μM. The detection limits for DA and UA were found to be 0.26 and 1.10 µM with CPE-SDS, whilst 0.22 and 0.38 µM with CPE-SDBS. The CPE-SDBS and CPE-SDS showed good reproducibility, repeatability, stability and high selectivity for determination of DA and UA in blood serum samples.