Open AccessChemical ionization mass spectrometry technique for detection of dimethylsulfoxide and ammonia
Author(s) -
Nowak J. B.,
Huey L. G.,
Eisele F. L.,
Tanner D. J.,
Mauldin R. L.,
Cantrell C.,
Kosciuch E.,
Davis D. D.
Publication year - 2002
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2001jd001058
Subject(s) - chemistry , mass spectrometry , ion , ammonia , protonation , reactivity (psychology) , ethanol , chemical ionization , molecule , analytical chemistry (journal) , acetone , ionization , organic chemistry , chromatography , medicine , alternative medicine , pathology
A chemical ionization mass spectrometer (CIMS) was used to study reactions of protonated ethanol clusters (C 2 H 5 OH) n H + with dimethylsulfoxide (DMSO), dimethylsulfone (DMSO 2 ), ammonia (NH 3 ), and a series of nonmethane hydrocarbons (NMHCs) and volatile organic compounds (VOCs). The reactivity of the (C 2 H 5 OH) n H + cluster ions is a function of cluster size with reactivity decreasing as cluster size increases. Ethanol cluster ion distributions that formed at atmospheric pressure from 24 ppbv, 900 ppmv, and 1% ethanol/N 2 gas mixtures were studied. Small (C 2 H 5 OH) n H + clusters, those formed using the 24 ppbv ethanol/N 2 mixture, react at or near the collisional rate with DMSO, NH 3 , acetone, and methyl vinyl ketone (MVK). The effective ion molecule rate coefficients are 1.8 × 10 −9 , 1.5 × 10 −9 , 1.0 × 10 −9 , and 1.6 × 10 −9 cm 3 molecule −1 s −1 , respectively. Only DMSO and NH 3 react efficiently with the two larger (C 2 H 5 OH) n H + cluster ion distributions studied. The effective rate coefficients for DMSO and NH 3 with the 900 ppmv ethanol cluster ion distribution are 1.5 × 10 −9 and 0.7 × 10 −9 cm 3 molecule −1 s −1 , respectively. The effective rate coefficient for DMSO with the 1% ethanol/N 2 mixture is 0.35 × 10 −9 cm 3 molecule −1 s −1 , while NH 3 reaches equilibrium with this cluster ion distribution. Experiments show that large (C 2 H 5 OH) n H + ion clusters must be used at relative humidities greater than 50% at 20°C to prevent formation of and subsequent interferences from H 3 O + ions. These results demonstrate that the (C 2 H 5 OH) n H + ion chemistry can selectively detect DMSO and NH 3 under most ambient atmospheric conditions with high sensitivity.