Laser ablation aerosol particle time-of-flight mass spectrometer (LAAPTOF): performance, reference spectra and classification of atmospheric samples

Shen, Xiaoli; Ramisetty, Ramakrishna; Mohr, Claudia; Huang, Wei; Leisner, Thomas; Saathoff, H.

doi:10.5194/amt-11-2325-2018

Cited by 28 publications

(67 citation statements)

References 53 publications

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“…Instruments tend to be custom-built, with examples including ATOFMS (Gard et al 1997;Pratt et al 2009b), SPLAT (Zelenyuk and Imre 2005;Zelenyuk et al 2015), ALABAMA (Brands et al 2011), and PALMS (Cziczo et al 2006;Thomson, Schein, and Murphy 2000). Some have been commercialized, e.g., ATOFMS (TSI), Livermore-SPAMS (Livermore Instruments, Oakland, California) (Frank et al 2011;Morrical, Balaxi, and Fergenson 2015), Hexin-SPAMS (Hexin Instrument Co, Ltd., Guangzhou, China) (Li et al 2011;Zhang et al 2012), and LAAPTOF (AeroMegt GmbH, Solingen, Germany) (Gemayel et al 2016;Shen et al 2018). The details of instrument construction, including the wavelength of the ionization laser, vary across different instruments, making direct spectral comparisons challenging.…”

Section: Mass Spectrometrymentioning

confidence: 99%

Real-time sensing of bioaerosols: Review and current perspectives

Huffman

Perring

Savage

et al. 2019

Aerosol Science and Technology

189

138

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Detection of bioaerosols, or primary biological aerosol particles (PBAPs), has become increasingly important for a wide variety of research communities and scientific questions. In particular, real-time (RT) techniques for autonomous, online detection and characterization of PBAP properties in both outdoor and indoor environments are becoming more commonplace and have opened avenues of research. With advances in technology, however, come challenges to standardize practices so that results are both reliable and comparable across technologies and users. Here, we present a critical review of major RT instrument classes that have been applied to PBAP research, especially with respect to environmental science, allergy monitoring, agriculture, public health, and national security. Eight major classes of RT techniques are covered, including the following: (i) fluorescence spectroscopy, (ii) elastic scattering, microscopy, and holography, (iii) Raman spectroscopy, (iv) mass spectrometry, (v) breakdown spectroscopy, (vi) remote sensing, (vii) microfluidic techniques, and (viii) paired aqueous techniques. For each class of technology we present technical limitations, misconceptions, and pitfalls, and also summarize best practices for operation, analysis, and reporting. The final section of the article presents pressing scientific questions and grand challenges for RT sensing of PBAP as well as recommendations for future work to encourage high-quality results and increased cross-community collaboration.

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Section: Mass Spectrometrymentioning

confidence: 99%

Real-time sensing of bioaerosols: Review and current perspectives

Huffman

Perring

Savage

et al. 2019

Aerosol Science and Technology

189

138

View full text Add to dashboard Cite

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“…The LAAPTOF has already been described in several other publications (Gemayel et al, 2016;Marsden et al, 2016;Shen et al, 2018) and therefore here we will especially focus on those aspects related to its operation with the fs laser. The LAAPTOF consists of four major modules: an aerodynamic lens focusing incoming particles into a narrow beam, the sizing section with two ultraviolet (UV) 405 nm continuouswave detection laser diodes (DL1, DL2) set 11.3 cm apart from each other, the laser ablation/particle ionization region, and a bipolar time-of-flight mass spectrometer (Fig.…”

Section: Laaptofmentioning

confidence: 99%

“…In the sizing region, the time delay between the detection of the scattered laser light of DL1 and DL2 by photomultiplier tubes (PMT, Thorn EMI, UK, type 9781R) is used to calculate the size of particles in the range of 200-2500 nm. The particle size detection methods and detection efficiencies for the LAAPTOF have been described in several publications (Gemayel et al, 2016;Marsden et al, 2016;Shen et al, 2018). Shen et al (2018) show a comparison of the performance of the instrument we used in this study with other (some of them modified) LAAPTOF instruments.…”

Section: Laaptofmentioning

confidence: 99%

“…The particle size detection methods and detection efficiencies for the LAAPTOF have been described in several publications (Gemayel et al, 2016;Marsden et al, 2016;Shen et al, 2018). Shen et al (2018) show a comparison of the performance of the instrument we used in this study with other (some of them modified) LAAPTOF instruments. The scattering signal from DL2 produces a 10 V transistor-transistor logic (TTL) electronic signal that triggers the 193 nm ns excimer laser (ArF, pulse width of 5-8 ns, adjustable pulse energy from 0 to 10 mJ, ATLEX-S, ATL Lasertechnik GmbH).…”

Section: Laaptofmentioning

confidence: 99%

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Exploring femtosecond laser ablation in single-particle aerosol mass spectrometry

et al. 2018

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Abstract. Size, composition, and mixing state of individual aerosol particles can be analysed in real time using singleparticle mass spectrometry (SPMS). In SPMS, laser ablation is the most widely used method for desorption and ionization of particle components, often realizing both in one single step. Excimer lasers are well suited for this task due to their relatively high power density (10 7 -10 10 W cm −2 ) in nanosecond (ns) pulses at ultraviolet (UV) wavelengths and short triggering times. However, varying particle optical properties and matrix effects make a quantitative interpretation of this analytical approach challenging. In atmospheric SPMS applications, this influences both the mass fraction of an individual particle that is ablated, as well as the resulting mass spectral fragmentation pattern of the ablated material. The present study explores the use of shorter (femtosecond, fs) laser pulses for atmospheric SPMS. Its objective is to assess whether the higher laser power density of the fs laser leads to a more complete ionization of the entire particle and higher ion signal and thus improvement in the quantitative abilities of SPMS. We systematically investigate the influence of power density and pulse duration on airborne particle (polystyrene latex, SiO 2 , NH 4 NO 3 , NaCl, and custom-made core-shell particles) ablation and reproducibility of mass spectral signatures. We used a laser ablation aerosol time-of-flight single-particle mass spectrometer (LAAPTOF, AeroMegt GmbH), originally equipped with an excimer laser (wavelength 193 nm, pulse width 8 ns, pulse energy 4 mJ), and coupled it to an fs laser (Spectra Physics Solstice-100F ultrafast laser) with similar pulse energy but longer wavelengths (266 nm with 100 fs and 0.2 mJ, 800 nm with 100 fs and 3.2 mJ). We successfully coupled the freefiring fs laser with the single-particle mass spectrometer employing the fs laser light scattered by the particle to trigger mass spectra acquisition. Generally, mass spectra exhibit an increase in ion intensities (factor 1 to 5) with increasing laser power density (∼ 10 9 to ∼ 10 13 W cm −2 ) from ns to fs laser. At the same time, fs-laser ablation produces spectra with larger ion fragments and ion clusters as well as clusters with oxygen, which does not render spectra interpretation more simple compared to ns-laser ablation. The idea that the higher power density of the fs laser leads to a more complete particle ablation and ionization could not be substantiated in this study. Quantification of ablated material remains difficult due to incomplete ionization of the particle. Furthermore, the fslaser application still suffers from limitations in triggering it in a useful time frame. Further studies are needed to test potential advantages of fs-over ns-laser ablation in SPMS.

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“…All instruments were set up in a temperature-controlled measurement container kept at ∼ 25 • C. The container has been described elsewhere Shen et al, 2018). All sampling inlets were located 3.7 m a.g.l.…”

Section: Measurement Sitementioning

confidence: 99%

Response to referee comments

Huang¹

2019

Preprint

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The chemical composition and volatility of organic aerosol (OA) particles were investigated during July-August 2017 and February-March 2018 in the city of Stuttgart, one of the most polluted cities in Germany. Total non-refractory particle mass was measured with a highresolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS; hereafter AMS). Aerosol particles were collected on filters and analyzed in the laboratory with a filter inlet for gases and aerosols coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (FIGAERO-HR-ToF-CIMS; hereafter CIMS), yielding the molecular composition of oxygenated OA (OOA) compounds. While the average organic mass loadings are lower in the summer period (5.1 ± 3.2 µg m −3 ) than in the winter period (8.4 ± 5.6 µg m −3 ), we find relatively larger mass contributions of organics measured by AMS in summer (68.8±13.4 %) compared to winter (34.8±9.5 %). CIMS mass spectra show OOA compounds in summer have O : C of 0.82±0.02 and are more influenced by biogenic emissions, while OOA compounds in winter have O : C of 0.89±0.06 and are more influenced by biomass burning emissions. Volatility parametrization analysis shows that OOA in winter is less volatile with higher contributions of low-volatility organic compounds (LVOCs) and extremely low-volatility organic compounds (ELVOCs). We partially explain this by the higher contributions of compounds with shorter carbon chain lengths and a higher number of oxygen atoms, i.e., higher O : C in winter. Organic compounds desorbing from the particles deposited on the filter samples also exhibit a shift of signal to higher desorption temperatures (i.e., lower apparent volatility) in winter. This is consistent with the relatively higher O : C in winter but may also be related to higher particle viscosity due to the higher contributions of larger-molecular-weight LVOCs and ELVOCs, interactions between different species and/or particles (particle matrix), and/or thermal decomposition of larger molecules. The results suggest that whereas lower temperature in winter may lead to increased partitioning of semi-volatile organic compounds (SVOCs) into the particle phase, this does not result in a higher overall volatility of OOA in winter and that the difference in sources and/or chemistry between the seasons plays a more important role. Our study provides insights into the seasonal variation of the molecular composition and volatility of ambient OA particles and into their potential sources.

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Laser ablation aerosol particle time-of-flight mass spectrometer (LAAPTOF): performance, reference spectra and classification of atmospheric samples

Cited by 28 publications

References 53 publications

Real-time sensing of bioaerosols: Review and current perspectives

Real-time sensing of bioaerosols: Review and current perspectives

Exploring femtosecond laser ablation in single-particle aerosol mass spectrometry

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