Particle beam glow discharge mass spectrometry: spectral characteristics of nucleobases

Abstract

Use of a particle beam glow discharge (PB-GD) source for mass spectrometric determinations of deoxy- and ribonucleosides and nucleotides is described. Use of this combination of sample introduction and ion source decouples the vaporization and ionization steps, leading to very simple spectral structure. The mass spectra of these compounds are EI-like in nature, with clearly identified molecular ions and fragmentation patterns that are easily rationalized. The PB-GDMS combination can be operated in a flow injection mode wherein the analyte is injected directly into the solvent flow, or can also be coupled to a high-performance liquid chromatography (HPLC) system allowing LC/MS analysis of mixtures. Mass spectra obtained for nucleic acid bases, nucleosides, and nucleotides are readily obtained with injections of low-nanomole quantities. Representative PB-GDMS spectra for deoxy- and ribonucleosides, nucleotides, and mixed-base oligonucleotides are presented to demonstrate the capabilities of the GD source. Characteristic fragmentation peaks from the spectra of adenine, cytosine, guanine, and thymine were identified in 22-base sequences of single-stranded DNA. The PB-GD source is capable of producing spectra that may be used to identify the individual bases present in mixed-base DNA and RNA fragments.

Conversion of a commercial gas chromatography-mass spectrometer to a liquid chromatography-particle beam/glow discharge mass spectrometer

“…1. 5,9,18,19 Other types of metal cathodes have been explored and copper cathodes were found to provide the best sensitivity and offer fragmentations similar to those of EI sources. 18 The cathode assembly is fixed to a standard Agilent CI source body by custom tooling.…”

“…For GD sources, particles have to enter the source volume, and be vaporized to put analyte species in the gas phase for excitation/ ionization and subsequent detection. 5,19,25 This process can occur by either sputtering off of the cathode surface or vaporization from the heated walls of the source volume. With previous PB/ GDMS work, it was thought that the particles were required to hit the cathode, 12 and so this source was designed with this in mind.…”

“…4 Glow discharge sources used with MS analyzers provide the ability to obtain both elemental and molecular information simultaneously when coupled with gas and liquid chromatography (GC and LC) separations. [5][6][7][8][9] While gaseous introduction into a GD source is relatively straightforward, the presence of residual solvents from a liquid originating sample is deleterious to source performance. 10,11 The ability to directly introduce liquid samples into a GD source is made possible by utilizing particle beam (PB) technology, 12 a transport-type LC-MS interface originally introduced by Willoughby and Browner.…”

Selenium speciation by liquid chromatography-particle beam/mass spectrometry (LC-PB/MS): application to a yeast reference material and synthetic urine

“…Previous work in this laboratory involved the liquid chromatography particle beam mass spectrometry (LC-PB/MS) system for the analysis of a large number of organic, inorganic, organometallic and biological compounds in neat solutions and real world samples such as botanical products (e.g., green tea, echinacea, kelp) using interchangeable ionization sources (electron ionization and glow discharge). 23,24,26,[29][30][31] The PB interface treats analytes in a GC-style by converting them into the gas phase prior to ionization. The primary quality of this approach is that typical LC eluents (meaning ow rate, composition and polarities) are directed to low pressure (<10 À3 Torr) ionization sources without any remnants of the LC solvents.…”

Organic and inorganic arsenic speciation through ion exchange chromatography with particle beam-glow discharge mass spectrometry detection

“…Earlier speciation work in this group has demonstrated the merit of the PB-GDMS method in the analysis of selenoamino acids and alkyllead compounds. [21][22][23] In addition to this work, the particle beam interface has also been used in a hollow cathode glow discharge optical emission (PB/HC-OES) instrument. [24][25][26][27][28][29][30][31][32] Organic and inorganic selenium compounds were separated and detected with nanogram detection limits using the PB/HC-OES.…”