Ubiquinone electrochemistry in analysis and sensing

Ubiquinone (UQ) is a lipophilic compound present in most living organisms, where UQ's interesting but complex electrochemistry serves an important role in the transfer of electrons and protons within and across the mitochondrial membrane. We briefly review the electrochemical characteristics of UQ and its reduced state, ubiquinol, in solution and immobilized on electrodes, together with its application in electrochemical sensing and detection systems, for example, measuring redox status with reference to reactive oxidative species. The importance of the local environment, solvent, electrolyte, organic membrane, and pH, on the electrochemical behavior of UQ, is also discussed. We discuss techniques used for the direct detection of UQ such as liquid chromatography-electrochemistry. Mediated electrochemistry of UQ allows for quantitative measurements of ions, small molecules, and other analytes such as glucose via chemical sensors and biosensors.