Portable instrument for electrochemical gas sensing

The instrument features up to four individual sensors, which may be used in the amperometric or voltammetric mode. A small pump is employed in order to make use of the enhanced sensitivity obtained with active transport of the sample gas to the sensor membranes. A Pt/air system serves as reference electrode. For the amperometric detection of acetaldehyde, as an example, a detection limit of 12 ppb was obtained. Several approaches to optimize selectivity and sensitivity are demonstrated on the portable, battery powered instrument. These include the use of a preconcentration trap for acetaldehyde and of chemical filters for the elimination of the interference of ozone on the measurement of NO, as well as voltammetric and concurrent measurements from two sensors in order to determine both NO and SO₂ in mixtures.