Amperometric biosensor for formic acid in air

The possibility of developing a simple, inexpensive and specific personal p assive "real-time" air sampler incorporating a biosensor for formic acid wa s investigated. The sensor is based on the enzymatic reaction between formi c acid and formate dehydrogenase (FDH) with nicotinamide adenine dinucleoti de (NAD(+)) as a co-factor and Meldola's blue as mediator. An effective way to immobilise the enzyme, co-factor and Meldola's blue on screen-printed, disposable, electrodes was found to be in a mixture of glycerol and phospha te buffer covered with a gas-permeable membrane. Steady-state current was r eached after 4-15 min and the limit of detection was calculated to be below 1 mg/m(3). However, the response decreased by 50% after storage at -15 deg reesC for 1 day. (C) 2000 Elsevier Science B.V. All rights reserved.