A comprehensive characterization of photoelectron resonance capture ionization aerosol mass spectrometry for the quantitative and qualitative analysis of organic particulate matter
International Journal of Mass Spectrometry, 258 (1-3):
120--133 (2006)Abstract
Photoelectron resonance capture ionization (PERCI), when coupled with thermal vaporization aerosol mass spectrometry (AMS) is found to be an excellent ionization method for the identification of particle-bound organics. While the qualitative analytical advantages of PERCI have been demonstrated previously, a comprehensive characterization of PERCI-AMS, which will be of paramount importance in developing the method to perform reliable quantitative measurements, is discussed here. A detailed analysis, based on photoelectron, gas phase, and particle phase measurements, of the behavior and limitations of PERCI-AMS is given. The performance of PERCI-AMS is affected by: delayed time between anion formation and extraction for mass spectral analysis, relative positioning of the vaporization probe (VP) and photoelectrode (PE), laser intensity, analyte pressure in the ionization region, particle matrix, and vaporization temperature ramping rate. Gas phase detection limits are found to be on the order of 107-109 cm-3 and particle phase detection limits for individual compounds are found to be on the order of 10-8-10-7 g of total sampled mass. An additional level of analyte selectivity is gained with the vapor pressure dependent desorption of deposited particles, achieved with ramped thermal vaporization. The major limitation of the thermal vaporization PERCI-AMS is the low duty cycle of the measurement, stemming from the pulsed nature of PERCI. Finally, prospects for improvements in detection limits as high as 3-4 orders of magnitude by adaptation of pulsed IR laser desorption to the system are discussed.