Carbon disulfide as a dopant in photon‐induced chemical ionization mass spectrometry. (13th August 2013)

• Record Type: Journal Article
• Authors: Dousty, Faezeh; O'Brien, Robert T.; Gahler, Roland; Kersten, Hendrik; Benter, Thorsten
• Is Part Of: Rapid communications in mass spectrometry. Volume 27:Number 17(2013)
• Page Start: 1969
• Page End: 1976
• Publication Date: 2013-08-13
• Subjects: Mass spectrometry -- Periodicals; 543.65
• DOI: 10.1002/rcm.6644
• Languages: English
• ISSNs: 0951-4198

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="rcm6644-sec-0001" sec-type="section"> <title>RATIONALE</title> <p>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<sub>2</sub>) 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.</p> </sec> <sec id="rcm6644-sec-0002" sec-type="section"> <title>METHODS</title> <p>The ability of CS<sub>2</sub> 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]<sup>+</sup> ions relative to [M+H]<sup>+</sup> 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.</p> </sec> <sec id="rcm6644-sec-0003" sec-type="section"> <title>RESULTS</title> <p>The results show that CS<sub>2</sub> increases the ionization efficiency of most of the analytes studied in this work comparably to toluene and anisole. CS<sub>2</sub> promotes both ionization routes of [M]<sup>+</sup> and [M+H]<sup>+</sup>. In addition, due to the higher ionization energy (IE) of CS<sub>2</sub> (10.01) compared to the IEs of toluene (8.83) and anisole (8.20), CS<sub>2</sub> can enhance the ionization efficiency of analytes that cannot be enhanced with toluene and anisole.</p> </sec> <sec id="rcm6644-sec-0004" sec-type="section"> <title>CONCLUSIONS</title> <p>We have determined that CS<sub>2</sub> is a viable dopant for use in APPI sources. For some analytes, significant [M+H]<sup>+</sup> ion signals are observed; therefore, the donated proton must come from either water clusters or solvents. In addition, CS<sub>2</sub> promotes the ionization of analytes with low PAs and higher IEs than that of toluene and anisole. Copyright © 2013 John Wiley & Sons, Ltd.</p> </sec> </abstract>