Selective detection of alkanolamine vapors by ion mobility spectrometry with ketone reagent cases

The ion mobility (IMS) spectra of the alkanolamines, monoethanolamine (MEA) , 3-amino-1-propanol (PRA), 4-amino-1-butanol (BUA), and 5-amino-1-pentanol (PEA) with acetone and 4-heptanone reagent gases have been measured using a hand-held spectrometer. Monomer and dimer peak patterns were observed for all the alkanolamines with acetone reagent gas. Drift times of monomer and dimer ion clusters for each alkanolamine increased linearly in order of si ze of alkyl group. Ammonia, Freon 22, and F76 diesel vapors, having similar or coincident mobilities, caused severe interference, Replacement of aceto ne with 4-heptanone reagent gas resulted in good separation by the altering drift times of product ions. The limit of detection was 0.005 ppm having a linear range of 0.005-0.7 ppm, and signal saturation occurred above 0.88 p pm. Detection was reversible, with a response time of 4 min and a slower re covery time of > 60 min, at vapor levels of 0.7 ppm and ambient nozzle and drift-region temperatures. In contrast to acetone chemistry, single-peak pa tterns were observed for the alkanolamines with the 4-heptanone reagent. Fu rther, drift times unexpectedly remained stagnant with increasing alkyl-gro up size. From atmospheric pressure chemical ionization (APcI) tandem mass s pectral identifications and collision induced studies, dynamic changes in p roduct-ion equilibria in the LMS drift region compensated by differences in collision cross sections were suggested as the governing causes of the unu sual mobility effect.