Isoprene measurement by ozone-induced cherniluminescence

An instrument has been constructed that monitors gaseous isoprene continuously. The basis for detection is chemiluminescence with ozone. The isoprene/ozone reaction produces electronically excited formaldehyde whose subsequent emission to the ground state is viewed with a blue-sensitive photomultiplier tube. The instrument has a response time of 0.1 s, is linear over 3 orders of magnitude, and has a detection limit for isoprene of 400 pptv (at S/N = 2 and 5-s electronic time constant). Selectivities over various alkenes and other compounds are presented. The first real-time isoprene fluxes from oak leaves, using a single living leaf, are measured as a function of light modulation.