Chemical discrimination of the particulate and gas phases of miniCAST exhausts using a two-filter collection method

Abstract

Abstract. Combustion of hydrocarbons produces both particulate- and gas-phase emissions responsible for major impacts on atmospheric chemistry and human health. Ascertaining the impact of these emissions, especially on human health, is not straightforward because of our relatively poor knowledge of how chemical compounds are partitioned between the particle and gas phases. Accordingly, we propose coupling a two-filter sampling method with a multi-technique analytical approach to fully characterize the particulate- and gas-phase compositions of combustion by-products. The two-filter sampling method is designed to retain particulate matter (elemental carbon possibly covered in a surface layer of adsorbed molecules) on a first quartz fiber filter while letting the gas phase pass through and then trap the most volatile components on a second black-carbon-covered filter. All samples thus collected are subsequently subjected to a multi-technique analytical protocol involving two-step laser mass spectrometry (L2MS), secondary ion mass spectrometry (SIMS), and micro-Raman spectroscopy. Using the combination of this two-filter sampling–multi-technique approach in conjunction with advanced statistical methods, we are able to unravel distinct surface chemical compositions of aerosols generated with different set points of a miniCAST burner. Specifically, we successfully discriminate samples by their volatile, semi-volatile, and non-volatile polycyclic aromatic hydrocarbon (PAH) contents and reveal how subtle changes in combustion parameters affect particle surface chemistry.

A comparative study on effective density, shape factor, and volatile mixing of non-spherical particles using tandem aerodynamic diameter, mobility diameter, and mass measurements

“…A Nano-MOUDI cascade impactor and a combination of a nano-DMA and a nanometer aerosol sampler (NAS) were used to collect size-selected particles. A home-built doublefilter sampler (DFS) (Ngo et al, 2020) separated and collected both polydisperse particles and gasphase semi-volatiles.…”

“…Arrangement C (Figure 1) was used to collect samples for off-line chemical and morphological analyses. Polydisperse particles were collected on quartz-fiber filters (Pall Corp., Model TissuQuartz 2500QAT-UP) using a home-built double-filter sampler, which also separated and collected the gas-phase semi-volatiles (Ngo et al, 2020). Size-selected particles by aerodynamic diameter were collected on aluminum foils with a micro-orifice uniform- Twin) operating at an accelerating voltage of 200 kV.…”

A mass defect–based approach for the automatic construction of peak lists for databases of mass spectra with limited resolution: Application to time‐of‐flight secondary ion mass spectrometry data

“…ToF-SIMS is a convenient test diagnostic because postionization dissociation reactions produce large numbers of fragment ions approximately homogeneously distributed 12 up to m/z 600. The chemical composition of combustion-generated aerosols has already been explored; therefore, the quality of the assignments is tested against the manually selected peaks.…”

“…Given the familiarity of our research group with combustion‐generated aerosols, 9–11 the data processing protocol is tested on a database of 126 mass spectra obtained from time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) analysis of the exhaust of a laboratory diesel miniCAST burner supplied with diesel B7 as fuel. ToF‐SIMS is a convenient test diagnostic because postionization dissociation reactions produce large numbers of fragment ions approximately homogeneously distributed 12 up to m / z 600. The chemical composition of combustion‐generated aerosols has already been explored; therefore, the quality of the assignments is tested against the manually selected peaks.…”

Hydrogen, sp2 Carbon Hybridization, and sp2 Clustering as Pieces of the Puzzling Nanostructure of Soot: A Closer Look

“…Actually, it has been well assessed that techniques based on sublimation and laser heating, followed by mass spectrometry or imaging analysis of volatilized/condensed products, are suitable for analysis of PAHs adsorbed on soot or for the analysis of medium-high mass organic species like those constituting asphaltenes , and pitch . As matter of fact, sophisticated mass spectrometry methodologies have been developed for characterizing the particulate and gas-phase compositions of combustion byproducts, , and for distinguishing soot from OC in the carbon particles produced by a miniCAST soot generator . Laser desorption ionization time of flightmass spectrometry (LDI-TOFMS) directly applied on soot, devoid of OC, was ineffective, and some mass spectrometric signals, mainly due to soot fragmentation, could be detected only at high laser power …”