Determining Proton-Transfer Rate Constants for VOC's using the Protonated Acetone Reagent (2008)

Undergraduates: Jeremy Felton, Karen S. Wendling

Faculty Advisor: Gary Glish
Department: Chemistry

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Volatile organic compounds (VOCs) are found at low concentrations in the environment. Methods of detecting VOCs in air have been developed using mass spectrometry. Mass spectrometry detects gas-phase ions at low concentrations. One common method of ionizing VOCs uses proton-transfer ionization. Proton transfer reactions with high reaction rate constants can be used to detect low concentrations of VOCs. Proton-transfer rate constants have been experimentally determined in previous experiments for the reaction of hydronium ions with the VOCs isoprene, methyl vinyl ketone and methacrolein. Recent work has focused on the use of protonated acetone to ionize the VOC analytes via proton transfer to compare protonated acetone limits of detection to the limits of detection achieved using hydronium ion. Proton transfer rate constants for the reaction of protonated acetone with isoprene and methyl vinyl ketone were determined. Experimental results for the proton-transfer ionization reaction rate constant of isoprene and methyl vinyl ketone are 1.1 ± .4 x 10-9 and 5.5 ± .5 x 10-10 cm3/molecules-sec, respectively.