Doubly Modified Electrodes for the Selective Determination of Dopamine in the Presence of Interfering Species

Abstract

In this paper, we describe the double modification of the glassy carbon electrode surface with two polymer layers for the selective determination of dopamine. The first layer was the electropolymerized macrocyclic nickel complex acting as an electrocatalyst for the dopamine oxidation and the second layer the polyurethane benzyl l-glutamate (PUBLG) for screening interfering species. Hydrolyzed PUBLG (PU-C) showed a better screening effect. Thus prepared GC/Ni(II) complex film/PU-C electrodes exhibited improved selectivity and better performance than unmodified counterparts, with minimum passivation even in the presence of large excess of interferents. Under optimal conditions, these electrodes showed a linear response over a dopamine concentration range of 2.5 Â 10 À7 and 3.0 Â 10 À5 M with a correlation coefficient of 0.999 and detection limit (at S/N ¼ 3) of 8.0 Â 10 À8 M. The recoveries of dopamine in the 5-fold diluted human urine sample were 96.9% for 4 measurements. The rate constant for the dopamine oxidation measured by the rotating disk electrode was found to be 1.1 Â 10 À3 cm s À1.

3-mercaptopropylphosphonic acid modified gold electrode for electrochemical detection of dopamine

“…interference of Ca 2+ ) is the formation of calcium organic phosphonate at the modified surface, which decreases the attraction interaction between the negatively charged MPPA layer and the positively charged DA molecule. It is obvious that the interference from epinephrine could not be eliminated due to the structural similarity with DA [41].…”

Electropolymerization of negatively charged Ni(II) complex for the selective determination of dopamine in the presence of ascorbic acid

“…One way to solve this problem was to form a second layer over the nickel complex layer to block the entrance of AA to the electrode. Negatively charged polyurethane or Nafion films not only provided selectivity toward DA by effectively removing AA interference due to the electrostatic repulsion at neutral pH, but also offered additional advantages such as better stability and reproducibility over unmodified electrodes [40].…”

Selective detection of dopamine using a combined permselective film of electropolymerized (poly-tyramine and poly-pyrrole-1-propionic acid) on a boron-doped diamondelectrode

“…Of also interest is the modification of glassy carbon (GC) with two polymer layers for the selective determination of DA. 30 The first layer was the electropolymerized macrocyclic nickel complex acting as an electrocatalyst for the dopamine oxidation and the second layer the polyurethane benzyl L-glutamate (PUBLG) for screening interfering species. The hydrophobic PUBLG film was rendered to be more hydrophilic by immersing the electrode in a 1 : 3 (v/v) mixture of 4.0 M NaOH and methanol for 7 min at room temperature.…”