Phospholipid-modified carbon fiber brush electrode for the detection of dopamine and 3,4-dihydroxyphenylacetic acid

Abstract

Different procedures for modification of carbon fiber brush electrode (CFBE) with phospholipids were investigated using cyclic voltammetry and electrochemical impedance spectroscopy. Simple immersion of the preanodized electrode into hexane solution of asolectin (a mixture of soybean phospholipids) followed by formation of the phospholipid layer in NaCl solution was the most effective procedure. Phospholipid layer-modified electrode (PL-CFBE) was applied to detect dopamine and its metabolite, 3,4 dihydroxyphenylacetic acid, using differential pulse and square-wave voltammetry in phosphate buffer solution of pH 6.5. Accumulation of dopamine, supported by electrostatic interactions between positively charged amino group and negatively charged phosphate moiety of the layer, enhanced sensitivity of PL-CFBE compared to bare CFBE. On the contrary, repulsive interaction between 3,4 dihydroxyphenylacetate anion and negatively charged phosphate moiety of the layer suppressed PL-CFBE sensitivity, measured as a slope of calibration dependence.