Structure elucidation of geoporphyrins by desorption tandem mass spectrometry: Carbon-number, pyrrolic structure, and sequence information from one experiment

Conference · Wed Mar 01 04:00:00 EST 1989 · American Chemical Society, Division of Petroleum Chemistry, Preprints; (USA)

OSTI ID:7183256

Beato, B D; Yost, R A ^[1]; Quirke, J M.E. ^[2]

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1. Univ. of Florida, Gainesville (USA)
2. Florida International Univ., Miami (USA)

Tandem mass spectrometry (MS/MS) is a valuable tool in the structure elucidation of geoporphyrins. However, separate MS/MS experiments with a variety of ionization techniques (EI, PCI, and NCI) are usually required to determine carbon-number distribution, identify peripheral substituents and sequence the pyrroles. The authors have developed an MS/MS technique in which all three types of information are obtainable in a single experiment. The sample is introduced on the filament of a temperature programmable direct exposure probe (DEP) under hydrogen CI (H{sub 2}CI) conditions into a triple quadrupole mass spectrometer. As the filament heats up, the porphyrins vaporize, either to be ionized in the H{sub 2} plasma, or to recondense on cooler surfaces within the ion source. The positive molecular ions which form are selected to undergo collisionally activated dissociation (CAD) wih Ar, resulting in cleavage of peripheral substituents, to permit their identification. Negative molecular ions may also be monitored simultaneously to provide carbon-number information, as they do not fragment appreciably under these conditions. Once all of the sample has vaporized off of the DEP filament, the Ar is turned off and the instrument is switched under data system control to scan for only positive ions. As the DEP filament continues heating to temperatures exceeding 1300{degree}C, other surfaces within the ion source heat up, causing surface-induced decomposition of the recondensed porphyrins followed by vaporization and chemical ionization of the decomposition products to form mono- and di-pyrrolic ions. The application of this technique to the characterization of porphyrins will be discussed.

• OSTI ID: 7183256
• Report Number(s): CONF-8904127--
• Conference Information: Journal Name: American Chemical Society, Division of Petroleum Chemistry, Preprints; (USA) Journal Volume: 34:1
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
58 GEOSCIENCES
580000 -- Geosciences
CARBOXYLIC ACIDS
CHEMISTRY
GEOCHEMISTRY
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
MASS SPECTROSCOPY
MOLECULAR STRUCTURE
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PORPHYRINS
SPECTROSCOPY
TEMPERATURE EFFECTS