Simultaneous online detection of isoprene and isoprene-d2 using infrared photoacoustic spectroscopy

A photoacoustic spectrometer for the simultaneous detection of isoprene and the deuterated species [4,4-H-2]-2-methyl-1,3-butadiene (isoprene-d(2)) is presented. Using a sealed-off 13 CO2 laser a single-component detection limit of 400 ppt (isoprene) and 600 ppt (isoprene-d2) was achieved. Simultaneous monitoring of both compounds allowed the detection of labelling levels down to 6% (isoprene-d(2) in total isoprene) with a time resolution of 3 min. In emission studies with Eucalyptus globulus, the deuterated precursor [4,4-H-2]-1-deoxy-D-xylulose was fed to a leaf through the transpiration stream. Emission of isoprene-d(2) started as early as 10 min after application of the precursor.