Electrospray ionization mass spectrometric analyses of rhodium tetraphenylporphyrin complexes as electrocatalysts for CO oxidation by tandem mass spectrometry and hyphenated method with capillary electrophoresis

Abstract

Carbon monoxide (CO) poisoning of platinum (Pt)-based electrocatalysts is a huge obstacle in the development of proton-exchange membrane fuel cells. Fuel cell performance can be improved by removing CO through electrolytic oxidation. Yamazaki et al. synthesized several rhodium (Rh) tetraphenylporphyrin complexes as electrocatalysts to reduce CO poisoning. Experimental results showed that these complexes display higher electrochemical CO oxidation activity than previously synthesized Rh octaethylporphyrin complex and that the differences in the structures of p-substituted groups influence their activity. To confirm the formation of these Rh tetraphenylporphyrin complexes, analyses were performed using electrospray ionization mass spectrometry (ESI-MS), electrospray ionization tandem mass spectrometry (ESI-MS/MS), and capillary electrophoresis-electrospray ionization mass spectrometry (CE-ESI-MS). In ESI-MS, peaks other than that of the Rh tetraphenylporphyrin complex were occasionally detected at different m/z values. The ESI-MS/MS and CE-ESI-MS results suggest that these peaks correspond to the complexes coordinating CO or other ions, or to remaining uncoordinated tetraphenylporphyrins. Coordination of CO is supported by the ESI-MS/MS results for the Rh octaethylporphyrin complex. Separation of the uncoordinated tetraphenylporphyrin from Rh tetraphenylporphyrin complex was achieved by CE-ESI-MS.

Growing trend of CE at the omics level: The frontier of systems biology – An update

“…MALDI‐TOF‐MS offers high selectivity, mass accuracy, and sensitivity, and its mass spectra are often more easily interpreted than ESI spectra because most analyte ions are only single‐charged ions. Therefore, a number of papers report the use of CE in conjunction with MALDI 22, 23, but ESI is considered the major ionization source for interfacing CE to MS 24, 25. Interfaces are needed to transfer analytes from the liquid phase of CE to the gas phase for MS analysis.…”

CE of inorganic species – A review of methodological advancements over 2009–2010

“…This highlights the importance of selecting appropriate non‐denaturing conditions to obtain reliable structural information about non‐covalent metal–protein species by CE‐ESI‐MS. Other accounts of using CE‐ESI‐MS in the area involve testing various ligands of different complexing ability for their effect on the separation of trivalent lanthanides and the stability of the resulting complexes in ESI‐MS 184, investigation of intermediates involved in the photochemical formation of a Mo‐blue nanoring 185, and confirmation of the formation of Rh–tetraphenylporphyrin complexes coordinating CO and other species 186.…”

Atomic spectrometry update. Industrial analysis: metals, chemicals and advanced materials

“…392 Electrospray ionisation mass spectrometry (ESI-MS) yielded structural information on the macromolecules produced during the cell reactions. Proton exchange membrane fuel cells (PEMFC), fed with hydrogen/carbon monoxide or direct methanol fuel cells (fed with methanol), are recognised as very attractive devices to obtain electric energy directly via controlled oxidation of the fuel (hydrogen or methanol).…”

“…The use of rhodium porphyrin complexes as catalysts for increased carbon monoxide oxidation efficiency has been reported by Takeda and Yamazaki. 392 Electrospray ionisation mass spectrometry (ESI-MS) yielded structural information on the macromolecules produced during the cell reactions. The coordination of the carbon monoxide was determined using tandem ESI-MS/MS.…”