Electrochemical and Electrocatalytic Properties of Imidazole Analogues of the Redox Cofactor Pyrroloquinoline Quinone

• Published in: Electroanalysis (New York, N.Y.) Vol. 20; no. 20; pp. 2177 - 2184
• Main Authors: Lumibao, Claudine Y., Tillekeratne, L. M. Viranga, Kirchhoff, Jon R., Fouchard, David M. D., Hudson, Richard A.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01-10-2008; WILEY‐VCH Verlag
• Subjects: Electrochemical sensor; o-Quinone electrocatalysts; Pyrroloquinoline quinone; Thiol detection
• ISSN: 1040-0397; 1521-4109
• DOI: 10.1002/elan.200804315

The electrochemical and electrocatalytic properties of two synthetic imidazole analogues of the redox cofactor pyrroloquinoline quinone (PQQ) were evaluated. Cyclic voltammetry measurements as a function of pH indicated that both 4,5‐dihydro‐4,5‐dioxo‐1H‐imidazolo[5,4‐f]quinoline‐7,9‐dicarboxylic acid (1) and 4,5‐dihydro‐4,5‐dioxo‐2‐methyl‐1H‐imidazolo[5,4‐f]quinoline‐7,9‐dicarboxylic acid (2) undergo a reversible reduction of the o‐quinone moiety below pH 8 with potentials slightly more positive than those observed for PQQ. Upon incorporation into a polypyrrole membrane on the tip of a glassy carbon electrode, 1 and 2 exhibited electrocatalytic properties sufficient for the indirect amperometric detection of cysteine. The response for cysteine was linear up to 1 mM over a wide pH range. Detection limits (S/N=3) were in the μM range and dependent on the solution pH. Interference from redox active species such as dopamine and uric acid were minimized by the pH‐dependent redox potentials of 1 and 2 and thus the ability to tune the detection potential.