A thermal-dissociation–cavity ring-down spectrometer (TD-CRDS) for the detection of organic nitrates in gas and particle phases

[摘要] A thermal-dissociation–cavity ring-down spectrometer (TD-CRDS) was developed to measure NO 2 , peroxy nitrates (PNs), alkyl nitrates (ANs), and HNO 3 in the gas and particle phase, built using a commercial Los Gatos Research NO 2 analyzer. The detection limit of the TD-CRDS is 0.66 ppb for ANs, PNs, and HNO 3 and 0.48 ppb for NO 2 . For all four classes of NO y , the time resolution for separate gas and particle measurements is 8 min, and for total gas + particle measurements it is 3 min. The accuracy of the TD-CRDS was tested by comparison of NO 2 measurements with a chemiluminescent NO x monitor and aerosol-phase ANs with an aerosol mass spectrometer (AMS). N 2 O 5 causes significant interference in the PN and AN channel under high oxidant concentration chamber conditions, and ozone pyrolysis causes a negative interference in the HNO 3 channel. Both interferences can be quantified and corrected for but must be considered when using TD techniques for measurements of organic nitrates. This instrument has been successfully deployed for chamber measurements at widely varying concentrations, as well as ambient measurements of NO y .

[学科分类] 内科医学