Development of a volatility and polarity separator (VAPS) for volatility- and polarity-resolved organic aerosol measurement

Abstract

Discrepancies between modeled and measured atmospheric organic aerosol (OA) have highlighted the need for in situ instrumentation to better characterize the sources, formation mechanisms, and atmospheric evolution of ambient OA. We have developed the Volatility and Polarity Separator (VAPS) for hourly measurements of volatility-and polarity-resolved OA detected using highresolution time-of-flight mass spectrometry (HR-ToF-MS). Here, atmospheric OA is inertially impacted onto a collection cell, material is transferred onto a short transfer line located inside a gas chromatography (GC) oven, the oven is heated to provide a first-dimension separation of volatility, then thermally pulsed through a short polar GC column for a second-dimension polarity separation, and finally detected by HR-ToF-MS. This novel instrument increases the mass throughput of ambient OA in comparison to traditional GC due to shorter transfer paths and passivated coatings. Molecular separation resolution is partially sacrificed for this increased mass recovery, but the highresolution mass spectral data recovers information such as chemical classes and even some individual compounds along with elemental composition to determine aerosol oxidation states. Different techniques for interpreting and representing VAPS data are considered and its applicability to positive matrix factorization (PMF) analysis is demonstrated.

High time-resolved measurement of stable carbon isotope composition in water-soluble organic aerosols: method optimization and a case study during winter haze in eastern China

“…hydrophilic nature, WSOC has a great impact on the hygroscopic properties of aerosols and promotes the increase of cloud condensation nuclei (CCN) activity (Asa-Awuku et al, 2011). WSOC is a contributor to cardiovascular and respiratory problems because it is easy to be incorporated in biological systems such as human blood and lungs (Mills et al, 2009). WSOC can be emitted as primary organic carbon (POC) and secondary organic carbon (SOC) produced from atmospheric oxidation of volatile organic compounds (VOCs) (Sannigrahi et al, 2006;Weber et al, 2007;Zhang et al, 2018).…”

Comparison of three aerosol chemical characterization techniques utilizing PTR-ToF-MS: a study on freshly formed and aged biogenic SOA

“…Techniques like the TAG have been applied utilizing a gas chromatograph to provide non-polar and low-polarity tracers identification, while the modified semi-volatile TAG (SV-TAG) has broadened this range to highly polar oxygenates, mostly seen in the atmosphere, by using online derivatization (Isaacman et al, 2014;Zhao et al, 2013). The volatility and polarity separator (VAPS) is a similar technique that provides volatility-and polarity-resolved OA information by using a modified two-dimensional gas chromatography (2D-GC) approach combined with high-resolution time-of-flight mass spectrometry (Martinez et al, 2016). Although these techniques provide chemical speciation and lower time resolution, they can only do so for a small fraction of the OA mass (10-40 %).…”

Water-soluble organic carbon (WSOC) and its temperature-resolved carbon fractions in atmospheric aerosols in Beijing

“…Limited studies (Matsumoto et al, 2014;Yu et al, 2004) have been done to demonstrate that the thermal characteristics of WSOC altered with the particle size and sampling season, and that the thermal characteristics may reflect the formation processes and sources of the WSOC. Therefore, the data about temperature-resolved carbon fractions of WSOC may provide useful information to model simulations to estimate secondary organic carbon formation and assess their effects on climate and air quality (Martinez et al, 2016).…”