Sub-parts per billion detection of isoprene using a reduction gas detector with a portable gas chromatograph

Isoprene, a biogenic hydrocarbon emitted from vegetation, has been detected at sub-ppb levels, using a commercially available reduction gas detector (RGD) with an isothermal, portable gas chromatograph. For 1 ml samples, a detection limit of 300–500 parts per trillion (over an order of magnitude less than the traditional gas chromatography-flame ionization detection technique [GC-FID]) was achieved. The detector response was linear up to 500 ppb. This technique (GC-RGD) is compared with GC-FID measurements in studies of ambient isoprene mixing ratios within and above an oak forest in northeastern U.S.A. Applications of laboratory studies of the mechanism of isoprene production at the leaf level are also discussed.