Amperometric enzyme-based biosensor for direct detection of formaldehyde in the gas phase:: Dependence on electrolyte composition

An enzymatic sensor detecting the analyte formaldehyde directly from the gas phase is under investigation. In contrast to existing systems, it enables the quantification of the analyte without prior sampling or accumulation and thus can be used as an online system to monitor the formaldehyde concentration in ambient air. The amperometric sensor depends on the enzymatic conversion of the analyte using formaldehyde dehydrogenase from P putida [EC. 1.2.1.46] as the recognition element. It shows a linear response curve up to 15 ppm, with a detection limit of 0.03 pm (S/N= 3). In order to optimize the sensor performance the electrolyte composition within the sensor was varied with respect to pH value, buffer concentration and the addition of Ca2+ and Mg2+ ions. To elucidate the influence of the mediator and the enzyme on the sensor performance the stability and activity of the electrochemical mediator and the enzyme alone was examined separately in these different electrolytes.