GADH screen-printed biosensor for gluconic acid determination in wine samples

Gluconate dehydrogenase (GADH) biosensors have been developed for the satisfactory determination of gluconic acid in wine samples, without any pretreatment. The biosensors have been fabricated by cross-linking immobilization of GADH onto screen-printed carbon electrodes, containing the mediator tetrathiafulvalene (TTF). Chronoamperograms have been registered at +100 mV vs. screen-printed Ag/AgCl electrode by successive additions of a gluconic acid solution in the concentration range from 9.0 to 131.4 μM. This method shows a reproducibility of 8.1% (n = 3) related to the slopes of these calibration curves and a repeatability of 3.2% (n = 5). The procedure has shown an average capability of detection of 9.0 μM for a probability of false positive and negative of 0.05. Wine samples have been analyzed with these biosensors, obtaining satisfactory results.