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Carbon disulfide as a dopant in photon‐induced chemical ionization mass spectrometry
Author(s) -
Dousty Faezeh,
O'Brien Robert T.,
Gahler Roland,
Kersten Hendrik,
Benter Thorsten
Publication year - 2013
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6644
Subject(s) - chemistry , photoionization , mass spectrometry , anisole , ionization , atmospheric pressure chemical ionization , electron ionization , analytical chemistry (journal) , direct electron ionization liquid chromatography–mass spectrometry interface , dopant , chemical ionization , ion , organic chemistry , chromatography , physics , optoelectronics , doping , catalysis
RATIONALE The addition of a dopant to an Atmospheric Pressure PhotoIonization (APPI) source of a mass spectrometer has been shown to enhance the degree of analyte ionization. A series of different dopants has been successfully utilized; however, there has been very little published on the characteristics of a good dopant. We have proposed carbon disulfide (CS 2 ) as a novel new dopant based on its absorption cross‐section for the VUV photon's energy used and its unique gas‐phase ion chemistry, notably the fact that it does not contain a proton. METHODS The ability of CS 2 to enhance the ionization effectiveness of APPI was tested by using a group of compounds that have different proton affinities (PAs) and electron affinities (EAs). These results were compared to results obtained using the commonly used dopants, toluene and anisole. Particular attention was paid to the formation of [M] + ions relative to [M+H] + ions. Mass spectra were collected using a Waters Quattro Premier liquid chromatography/tandem mass spectrometry (LC/MS/MS) system equipped with a commercial Photomate™ photoionization source. RESULTS The results show that CS 2 increases the ionization efficiency of most of the analytes studied in this work comparably to toluene and anisole. CS 2 promotes both ionization routes of [M] + and [M+H] + . In addition, due to the higher ionization energy (IE) of CS 2 (10.01) compared to the IEs of toluene (8.83) and anisole (8.20), CS 2 can enhance the ionization efficiency of analytes that cannot be enhanced with toluene and anisole. CONCLUSIONS We have determined that CS 2 is a viable dopant for use in APPI sources. For some analytes, significant [M+H] + ion signals are observed; therefore, the donated proton must come from either water clusters or solvents. In addition, CS 2 promotes the ionization of analytes with low PAs and higher IEs than that of toluene and anisole. Copyright © 2013 John Wiley & Sons, Ltd.