COMPARISON OF HYDROPEROXIDE MEASUREMENTS MADE DURING THE MAUNA-LOA-OBSERVATORY PHOTOCHEMISTRY EXPERIMENT 2

From the fall of 1991 through the summer of 1992 the Mauna Loa Observa tory Photochemistry Experiment 2 (MLOPEX 2) took place in Hawaii. The experiment consisted of four intensive research periods, each approxim ately 1 month in duration. We report a comparison of measurements of a tmospheric hydroperoxide and methylhydroperoxide as measured during ML OPEX 2a (September 16 to October 23, 1991) and MLOPEX 2b (January 15 t o February 15, 1992). The analytical techniques used for measuring hyd roperoxides included tunable diode laser infrared absorption (TDLAS) a nd fluorescence from an enzymatically produced dimer. The TDLAS techni que measured hydrogen peroxide (H2O2) only. Three different procedures were utilized to distinguish between H2O2 and organic hydroperoxides in the fluorescence analytical techniques. These were high performance liquid chromatographic (HPLC) separation, enzymatic discrimination, a nd differential aqueous solubility. The measured concentrations ranged from 0 to 2 parts per billion by volume (ppbv) for H2O2 and 0 to ppbv for methylhydroperoxide (CH3OOH). Depending on the time period of mea surement, the agreement varied between 20% and a factor of 2 or more f or the measurement of H2O2. The discrepancy for the CH3OOH data was la rger.