A novel inlet system for online chemical analysis of semi-volatile submicron particulate matter

摘要

We herein present a novel modular inlet system designed to be coupled tolow-pressure gas analyzers for online chemical characterization ofsemi-volatile submicron particles. The "chemical analysis of aerosolonline" (CHARON) inlet consists of a gas-phase denuder for stripping offgas-phase analytes, an aerodynamic lens for particle collimation combinedwith an inertial sampler for the particle-enriched flow and athermodesorption unit for particle volatilization prior to chemicalanalysis. The denuder was measured to remove gas-phase organics with anefficiency > 99.999% and to transmit particles in the100–750 nm size range with a 75–90% efficiency. The measuredaverage particle enrichment factor in the subsampling flow from theaerodynamic lens was 25.6, which is a factor of 3 lower than the calculatedtheoretical optimum.We coupled the CHARON inlet to a proton-transfer-reaction time-of-flight massspectrometer (PTR-ToF-MS) which quantitatively detects most organic analytesand ammonia. The combined CHARON-PTR-ToF-MS setup is thus capable ofmeasuring both the organic and the ammonium fraction in submicron particlesin real time. Individual organic compounds can be detected down to levels of10–20 ng m?3. Two proof-of-principle studies were carried out fordemonstrating the analytical power of this new instrumental setup:(i) oxygenated organics and their partitioning between the gas and theparticulate phase were observed from the reaction of limonene with ozone and(ii) nicotine was measured in cigarette smoke particles demonstrating thatselected organic target compounds can be detected in submicron particles inreal time.