Applications and limitations of constrained high-resolution peak fitting on low resolving power mass spectra from the ToF-ACSM

Abstract

Abstract. The applicability, methods and limitations of constrained peak fitting on mass spectra of low mass resolving power (m∕Δm50 ∼ 500) recorded with a time-of-flight aerosol chemical speciation monitor (ToF-ACSM) are explored. Calibration measurements as well as ambient data are used to exemplify the methods that should be applied to maximise data quality and assess confidence in peak-fitting results. Sensitivity analyses and basic peak fit metrics such as normalised ion separation are employed to demonstrate which peak-fitting analyses commonly performed in high-resolution aerosol mass spectrometry are appropriate to perform on spectra of this resolving power. Information on aerosol sulfate, nitrate, sodium chloride, methanesulfonic acid as well as semi-volatile metal species retrieved from these methods is evaluated. The constants in a commonly used formula for the estimation of the mass concentration of hydrocarbon-like organic aerosol may be refined based on peak-fitting results. Finally, application of a recently published parameterisation for the estimation of carbon oxidation state to ToF-ACSM spectra is validated for a range of organic standards and its use demonstrated for ambient urban data.

Measurements of higher alkanes using NO<sup>+</sup>PTR-ToF-MS: significant contributions of higher alkanes to secondary organic aerosols in China

“…A description of the algorithm can be found in Stark et al 2015and Timonen et al (2016). Figure 1 shows the high-resolution peak fitting to the averaged mass spectra on a typical day (12 October 2018) for m/z 169, m/z 211 and m/z 281, at which masses produced by dodecane (C12H25 + ), pentadecane (C15H31 + ) and eicosane (C20H41 + ) are detected.…”

Spatiotemporal Variation in Composition of Submicron Particles in Santiago Metropolitan Region, Chile

“…Submicron particle non-refractory species, such as organics, nitrate, sulfate, ammonium, and chloride, were monitored on a basis of 10-min time resolution using the aerosol chemical speciation monitor (ACSM, Aerodyne Research Inc, USA) and the time-of-flight ACSM (ToF-ACSM, Aerodyne Research Inc., USA). Extensive descriptions of the instruments are presented by Ng et al (2011), Fröhlich et al (2013, and Timonen et al (2016).…”

Supplementary material to "Observations of VOC emissions and photo chemical products over US oil- and gas-producing regions using high-resolution H<sub>3</sub>O<sup>+</sup> CIMS (PTR-ToF-MS)"

“…Although there is not yet a quantitative method to determine the extent and magnitude of peak overlap errors in every situation, Tofware provides qualitative assessment tools that rely on the dependence of peak-fitting error on mass calibration precision (Timonen et al, 2016). Several studies have suggested that mass calibration precision and accuracy are strong controls on peak fitting error (Corbin et al, 2015;Cubison and Jimenez, 2015).…”