PROTON TRANSFER REACTION MASS SPECTROMETRY 

Proton transfer reaction mass spectrometry (PTR-MS) is a chemical ionization mass spectrometry technique capable of quantifying volatile organic compounds (VOCs), in a gaseous sample at time resolutions down to a fraction of a second. The permanent constituents of air, oxygen, nitrogen, etc. are not detected by the PTR-MS. PTR-MS is suitable for the measurement of a range of atmospheric VOCs including aromatics, oxygenates, organo-sulphurs and terpenes. 
The PTR-MS operates with the aid of a custom built auxiliary rack that regulates the flow of air in the sample inlet and controls whether the PTR-MS is sampling ambient or zero air or calibration gas. During this study zero readings and calibrations against certified gas standards were performed on the PTR-MS several times per day. Four calibration standards were used during the study, diluted to atmospheric concentrations using a set of mass flow controllers and a mixing chamber in the auxiliary rack. The PTR-MS was calibrated for: formaldehyde, acetaldehyde, acrolein, methacrolein, acetone, methyl ethyl ketone, methanol, ethyl acetate, benzene, xylene, trimethyl benzene, isoprene, a-pinene, 1,8 cineole, dimethyl sulphide, acetonitrile and the mono-, di and tri-chlorobenzenes. Only m/z that were detected above the MDL greater than 25% of the time, and had peak to noise ratios greater than 5 (95th percentile/MDL) are reported. Further details are available in Galbally et al. (2007) and Dunne et al. (2012) 


Dunne, Erin, Galbally, Ian E., Lawson, Sarah, and Patti, Antonio (2012) Interference in the PTR-MS measurement of acetonitrile at m/z 42 in polluted urban air a study using switchable reagent ion PTR-MS, International Journal of Mass Spectrometry, 319320: 4047. http://dx.doi.org/10.1016/j.ijms.2012.05.004

Galbally, I. E., Lawson, S. J., Weeks, I. A., Bentley, S. T., Gillett, R. W., Meyer, M., and Goldstein, A. H. (2007). Volatile organic compounds in marine Air at Cape Grim, Australia. Environmental Chemistry, 4(3): 178182.

