Articles | Volume 9, issue 4
Research article
02 May 2016
Research article |  | 02 May 2016

The performance and the characterization of laser ablation aerosol particle time-of-flight mass spectrometry (LAAP-ToF-MS)

Rachel Gemayel, Stig Hellebust, Brice Temime-Roussel, Nathalie Hayeck, Johannes T. Van Elteren, Henri Wortham, and Sasho Gligorovski

Abstract. Hyphenated laser ablation–mass spectrometry instruments have been recognized as useful analytical tools for the detection and chemical characterization of aerosol particles. Here we describe the performances of a laser ablation aerosol particle time-of-flight mass spectrometer (LAAP-ToF-MS) which was designed for aerodynamic particle sizing using two 405 nm scattering lasers and characterization of the chemical composition of single aerosol particle via ablation/ionization by a 193 nm excimer laser and detection in a bipolar time-of-flight mass spectrometer with a mass resolving power of mm > 600.

We describe a laboratory based optimization strategy for the development of an analytical methodology for characterization of atmospheric particles using the LAAP-ToF-MS instrument in combination with a particle generator, a differential mobility analyzer and an optical particle counter. We investigated the influence of particle number concentration, particle size and particle composition on the detection efficiency. The detection efficiency is a product of the scattering efficiency of the laser diodes and the ionization efficiency or hit rate of the excimer laser. The scattering efficiency was found to vary between 0.6 and 1.9 % with an average of 1.1 %; the relative standard deviation (RSD) was 17.0 %. The hit rate exhibited good repeatability with an average value of 63 % and an RSD of 18 %. In addition to laboratory tests, the LAAP-ToF-MS was used to sample ambient air during a period of 6 days at the campus of Aix-Marseille University, situated in the city center of Marseille, France. The optimized LAAP-ToF-MS methodology enables high temporal resolution measurements of the chemical composition of ambient particles, provides new insights into environmental science, and a new investigative tool for atmospheric chemistry and physics, aerosol science and health impact studies.

Short summary
LAAP-ToF-MS has been optimized for particle size and number concentration evolution and characterization of the chemical composition of ambient particles by following specific ions. The advantage of this instrument is that it can analyze the ambient particles online and continuously. It is capable of analyzing inorganic material in ambient particles; in particular the presence of metals can be analyzed. Last but not least, it is a compact and easily transportable tool for field measurements.