A NEW CHEMICAL-IONIZATION MASS-SPECTROMETER TECHNIQUE FOR THE FAST MEASUREMENT OF GAS-PHASE NITRIC-ACID IN THE ATMOSPHERE

A new chemical ionization mass spectrometer (CIMS) technique has been developed for the measurement of HNO3. The technique has been field te sted and informally intercompared with a standard filter pack method, and a new CIMS technique developed by the National Oceanic and Atmosph eric Administration Aeronomy Laboratory. The technique has been shown under lab conditions to have sensitivities as high as 0.2 parts per tr illion volume (pptv) HNO3 for a 1 s integration of each the reagent an d product ions, with a typical clean air field detection limit of 1-3 pptv for the same integration times. The new technique also responds q uickly to changes in HNO3 concentrations. The high sensitivity and fas t response time make this technique well suited for airborne measureme nts.