COMBINED LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY OF TETRAPYRROLES OF SEDIMENTARY SIGNIFICANCE

The on-line coupling of a high-performance liquid chromatograph to a mass spectrometer (LC/MS) has allowed the analysis of a number of tetrapyrrole pigments of sedimentary significance. Mass spectra were obtained under conditions of discharge ionization and are characterized by the presence of protonated ion species (positive-ion mode) or molecular ions (negative-ion mode), respectively. Fragmentation processes were found to be restricted to the periphery of the structures. In the positive-ion mode the extent of fragmentation could be manipulated by alteration of the repeller voltage in the ion source, allowing molecular weight information to be obtained, as well as specific fragmentation patterns. These findings have suggested a number of applications of LC/MS in the investigation of sedimentary tetrapyrrole distributions. In particular, the assignment of individual components in mixtures without resort to their isolation is possible from comparison of mass spectra with those of authentic standards and from coinjection with the standards. © 1990, American Chemical Society. All rights reserved.