A method for extracting calibrated volatility information from the FIGAERO-HR-ToF-CIMS and its experimental application

Thomas J Bannan,Carl J Percival,Archit Mehra,Michael Priestley,M Rami Alfarra,Stephen D Worrall,Dave Topping,Ulrich K Krieger,Hugh Coe,Jonathan P Reid,Nicholas A Marsden,Gordon Mcfiggans,Michael Le Breton,Julia Hammes,Asan Bacak,Wade Robinson,Mattias Hallquist,John Jayne

doi:10.5194/amt-12-1429-2019

Abstract

Abstract. The Filter Inlet for Gases and AEROsols (FIGAERO) is an inlet specifically designed to be coupled with the Aerodyne High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (HR-ToF-CIMS). The FIGAERO-HR-ToF-CIMS provides simultaneous molecular information relating to both the gas- and particle-phase samples and has been used to extract vapour pressures (VPs) of the compounds desorbing from the filter whilst giving quantitative concentrations in the particle phase. However, such extraction of vapour pressures of the measured particle-phase components requires use of appropriate, well-defined, reference compounds. Vapour pressures for the homologous series of polyethylene glycols (PEG) ((H-(O-CH2-CH2)n-OH) for n=3 to n=8), covering a range of vapour pressures (VP) (10−1 to 10−7 Pa) that are atmospherically relevant, have been shown to be reproduced well by a range of different techniques, including Knudsen Effusion Mass Spectrometry (KEMS). This is the first homologous series of compounds for which a number of vapour pressure measurement techniques have been found to be in agreement, indicating the utility as a calibration standard, providing an ideal set of benchmark compounds for accurate characterization of the FIGAERO for extracting vapour pressure of measured compounds in chambers and the real atmosphere. To demonstrate this, single-component and mixture vapour pressure measurements are made using two FIGAERO-HR-ToF-CIMS instruments based on a new calibration determined from the PEG series. VP values extracted from both instruments agree well with those measured by KEMS and reported values from literature, validating this approach for extracting VP data from the FIGAERO. This method is then applied to chamber measurements, and the vapour pressures of known products are estimated.

Highlights

Trace gases and aerosol particles, from anthropogenic and natural sources, are important components of the Earth’s climate system, the components of which vary significantly in terms of properties such as volatility, affecting their impact on air quality and climate change (Glasius and Goldstein, 2016)
A single exponential fit to the data on the vapour pressures (VPs) at 298 K derived from the polyethylene glycols (PEG) series and extracted Tmax can provide a relationship between Tmax and VP: VP (Pa) = 0.2612exp−0.071Tmax, with Tmax in (◦C)
We present here the calibration of two FIGAERO inlets coupled to the ToF-CIMS for extracting volatility information from single-component and chamber measurements

Summary

Introduction

Trace gases and aerosol particles, from anthropogenic and natural sources, are important components of the Earth’s climate system, the components of which vary significantly in terms of properties such as volatility, affecting their impact on air quality and climate change (Glasius and Goldstein, 2016). Bannan et al.: Extracting calibrated volatility information from FIGAERO-HR-ToF-CIMS composition and properties of ambient atmospheric aerosol particles, including component vapour pressures (VPs; Bilde et al, 2015), that are required to predict their environmental and human health impacts. This is attributable in large part to the fact that a significant fraction of fine atmospheric aerosol particles are comprised of organic material (20 %–90 % of particle mass) (Jimenez et al, 2009), containing potentially thousands of mostly unidentified compounds with properties that are often not well known

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