Hofmeister Phenomena in Bioelectrochemistry: The Supporting Electrolyte Affects the Response of Glucose Electrodes

The faradaic response of ferrocene-methanol when used as a mediator for the catalytic oxidation of glucose by glucose oxidase was examined in a range of electrolytes. The response was modulated by the nature of the salt used. A two-fold difference was observed with the sodium salts of fluoride and thiocyanate, with a 24% difference between NaCl and KCl. The changes in the response can be explained by the Hofmeister effect, with specific ion effects arising between the mediator and the co-substrate binding pocket of the enzyme. Such differences can significantly affect the response of electrochemically mediated glucose biosensors and biofuel cells and emphasise the importance of carefully considering the solution conditions when evaluating the properties of glucose oxidase based biosensors and biofuel cells.