Improved Chemical Amplification Instrument by Using a Nafion Dryer as an Amplification Reactor for Quantifying Atmospheric Peroxy Radicals under Ambient Conditions

Abstract

In our previous work (Yang et al. Anal. Chem. 2018, 90 (5), 3307−3312), we reported that a large diameter Nafion dryer can be used in the PERCA (PEroxy Radical Chemical Amplification) technique to minimize the impact of water vapor on the chain length (CL). By using a Nafion dryer, the sample was first dried to a low relative humidity (RH) and was then drawn into a FEP (fluorinated ethylene propylene) flow reactor tube to start the amplification cycles for peroxy radical measurement. This method provides a promising and simple method to minimize the sensitivity of CL to water vapor. However, there is a trade-off between inlet radical losses and moisture removal efficiency under high ambient RH conditions. In this paper, we report a further improvement by removing the inlet Nafion dryer and using it directly as an amplifier. The sample was drawn into the Nafion dryer directly without preconditioning to reduce inlet losses; the amplification and HO 2 reformation cycles were started in the Nafion dryer. The CL value at 3% RH inlet was about 150. A linear relationship between CL and RH inlet up to 87% RH was observed. Low loss of the CL under high RH inlet (about 10% reduction at 87% RH) was achieved. As a result, the modified system can largely remove the uncertainty of the CL arising from water vapor under most ambient conditions.

Characterization of submicron particles by time-of-flight aerosol chemical speciation monitor (ToF-ACSM) during wintertime: aerosol composition, sources, and chemical processes in Guangzhou, China

“…Numerous studies were conducted to investigate chemical composition, sources, and secondary processes of PM through an AMS or ACSM. It has been shown that organics generally account for a large proportion of PM (Zhang et al, 2007;Aiken et al, 2009;Allan et al, 2010;DeCarlo et al, 2010;Lee et al, 2015;Bressi et al, 2016;. In previous studies, mass spectral signals were input into the positive matrix factorization (PMF) to explore source information of organic aerosols (Zhang et al, 2011).…”

Observationally Constrained Modeling of Peroxy Radical During an Ozone Episode in the Pearl River Delta Region, China

“…Finally, the low concentrations of peroxy radicals were converted through this amplification into high concentrations of NO 2 , which was measured by a portable broadband cavity‐enhancement spectrometer (BBCES) (Fang et al., 2017). The dual‐channel PERCA system could effectively reduce uncertainties in RO 2 * detection, such as the interference caused by the rapid fluctuation of ambient pollutants (e.g., NO 2 and O 3 ) and the influence of water vapor on the chain length (CL) (Chen et al., 2016; C. Q. Yang, et al., 2018, 2019). The precision of the PERCA system was approximately 0.4 pptv (1 σ , 21 s) for RO 2 * (Guo et al., 2020).…”

“…The dual-channel PERCA system could effectively reduce uncertainties in RO 2 * detection, such as the interference caused by the rapid fluctuation of ambient pollutants (e.g., NO 2 and O 3 ) and the influence of water vapor on the chain length (CL) (Chen et al, 2016;C. Q. Yang, et al, 2018C. Q. Yang, et al, , 2019.…”

“…The precision of the PERCA system was approximately 0.4 pptv (1 σ , 21 s) for RO 2 * (Guo et al., 2020). Detailed information on the PERCA system can be found elsewhere (C. Q. Yang, et al., 2018, 2019).…”

Characterization of submicron particles by Time-of-Flight Aerosol Chemical Speciation Monitor (ToF-ACSM) during wintertime: aerosol composition, sources and chemical processes in Guangzhou, China

“…Total peroxy radicals (RO2* = RO2 • + HO2) were measured by the peroxy radical chemical amplification technique at the same sampling site. The measurement technique and detailed results could be found in Yang et al (2018Yang et al ( , 2019).…”