Amperometric enzyme-based gas sensor for formaldehyde:: Impact of possible interferences

In this work, cross-sensitivities and environmental influences on the sensitivity and the functionality of an enzyme-based amperometric sensor system for the direct detection of formaldehyde from the gas phase are studied. The sensor shows a linear response curve for formaldehyde in the tested range (0-15 vppm) with a sensitivity of 1.9 mu A/ppm and a detection limit of about 130 ppb. Cross-sensitivities by environmental gases like CO2, CO, NO, H-2, and vapors of organic solvents like methanol and ethanol are evaluated as well as temperature and humidity influences on the sensor system. The sensor showed neither significant signal to CO, H-2, methanol or ethanol nor to variations in the humidity of the test gas. As expected, temperature variations had the biggest influence on the sensor sensitivity with variations in the sensor signal of up to 10% of the signal for 5 vppm CH2O in the range of 25-30 degrees C.