First field application of a thermal desorption resonance-enhanced multiphoton-ionisation single particle time-of-flight mass spectrometer for the on-line detection of particle-bound polycyclic aromatic hydrocarbons

Abstract

The on-line analysis of single aerosol particles with mass spectrometrical methods is an important tool for the investigation of aerosols. Often, a single laser pulse is used for one-step laser desorption/ionisation of aerosol particles. Resulting ions are detected with time-of-flight mass spectrometry. With this method, the detection of inorganic compounds is possible. The detection of more fragile organic compounds and carbon clusters can be accomplished by separating the desorption and the ionisation in two steps, e.g. by using two laser pulses. A further method is, using a heated metal surface for thermal desorption of aerosol particles. If an ultraviolet laser is used for ionisation, a selective ionisation of polycyclic aromatic hydrocarbons (PAH) and alkylated PAH is possible via a resonance-enhanced multiphoton-ionisation process. Laser velocimetry allows individual laser triggering for single particles and additionally delivers information on aerodynamic particle diameters. It was shown that particles deriving from different combustion sources can be differentiated according to their PAH patterns. For example, retene, a C(4)-alkylated phenanthrene derivative, is a marker for the combustion of coniferous wood. In this paper, the first field application of a thermal desorption resonance-enhanced multiphoton-ionisation single particle time-of-flight mass spectrometer during a measurement campaign in Augsburg, Germany in winter 2010 is presented. Larger PAH-containing particles (i.e. with aerodynamic diameters larger than 1 μm), which are suspected to be originated by re-suspension processes of agglomerated material, were in the focus of the investigation. Due to the low concentration of these particles, an on-line virtual impactor enrichment system was used. The detection of particle-bound PAH in ambient particles in this larger size region was possible and in addition, retene could be detected on several particles, which allows to identify wood combustion as generic source of these particles. The observed diurnal distribution of these larger particles, however, support the origin by traffic induced re-suspension of sedimented/agglomerated material.

Mass spectrometric approaches for chemical characterisation of atmospheric aerosols: critical review of the most recent advances

“…Current advances in aerosol MS instrumentation involving tunable vacuum ultraviolet (VUV) light from a synchrotron source, resonant capture of low-energy electrons and chemical ionisation have recently been reviewed. [35] More recently, Zimmermann et al [45] described the first field application of resonance-enhanced multiphoton ionisation (REMPI) using a UV laser combined with thermal desorption of the particulate matter. REMPI enables facile and selective multiphoton ionisation of aromatic compounds, resulting in sensitive detection of particle-bound polycyclic aromatic hydrocarbons (PAHs).…”

Photoionization and photofragmentation in mass spectrometry with visible and UV lasers

“…Retene, for instance, proved to be a reliable indicator for burned coniferous wood. In a 2010 measurement campaign, Oster et al () demonstrated that the TD‐REMPI‐SP‐ToFMS system is operational under field conditions. The campaign had been conducted in the German city of Augsburg during wintertime.…”

Organic molecular markers and signature from wood combustion particles in winter ambient aerosols: aerosol mass spectrometer (AMS) and high time-resolved GC-MS measurements in Augsburg, Germany

“…Additional online mass spectrometers were run during this campaign. They include an Alkali AMS (Svane et al, 2004(Svane et al, , 2009 for online potassium and sodium determination, a single-particle thermal-desorption laser mass spectrometer (TD-REMPI-SP-ToF-MS) (Bente et al, 2006) for polycyclic aromatic hydrocarbon (PAH) detection on single particles (Oster et al, 2011) and an AMS for local source apportionment set up in the mobile atmospheric pollution laboratory "MOSQUITA" ("Measurements Of Spatial QUantitative Imissions of Trace gases and Aerosols", Bukowiecki et al, 2002;Mohr et al, 2011). These data are presented in other studies (e.g.…”