Selective ionization by electron-transfer MALDI-MS of vanadyl porphyrins from crude oils

Elucidating the Geometric Substitution of Petroporphyrins by Spectroscopic Analysis and Atomic Force Microscopy Molecular Imaging

“…30,33 Hence, most studies have been conducted within the complex matrix of petroleum molecules, and methods are applied to study petroporphyrins without isolation. 34−36 Thus far, only a few petroporphyrins have been isolated sufficiently for their structure to be unambiguously characterized. 9,25,26 However, unambiguous assignment of the structures is essential to understand the details of the transformation of porphyrins as well as to address numerous remaining questions, including the pattern of aromatic condensation or naphthenic (cycloalkane ring) fusion onto the macrocyclic tetrapyrrole, the attachment of side chains or linkers and their locations, and heteroatom incorporation.…”

Advances and Challenges in the Molecular Characterization of Petroporphyrins

“…Ramírez-Pradilla et al 13 reported the liquid-liquid extraction of crude oil with acetonitrile and obtained fractions enriched in vanadium and nickel, followed by purification with high-performance thin-layer chromatography fractionation (HPTLC, aminopropyl-bonded silica) using DCM as the eluent. 13 The authors applied a novel MALDI matrix that favors electron-transfer reactions 87,88 coupled to molecule-level FT-ICR MS and simultaneously detected 518 molecular formulae (the highest number of Ni, VO, oxygenated and sulfur-containing porphyrins detected to date) in a single crude oil sample with MALDI FT-ICR MS. Interestingly, S-containing vanadyl porphyrins contain 6 more DBEs than porphyrins without sulfur, consistent with earlier reports. 31 Microwave irradiation.…”

“…70 Therefore, selective ionization by ET reactions is possible by selecting a matrix with an IE greater than that of the petroporphyrin homologous series while suppressing the ionization of molecules with a higher IE than the matrix in the crude oil sample. 121 Giraldo-Dávila et al 122 were the first to illustrate the selectivity of the ET approach in the analysis of two South American crude oils. The authors showed that petroporphyrins (IE 6.5 to 7.0 eV) were selectively ionized as radical cations in a MALDI-TOF instrument using a cyanophenylenevinylene derivative with an IE of 8.2 eV for the matrix.…”

High-Field (3.4 T) ENDOR Investigation of Asphaltenes in Native Oil and Vanadyl Complexes by Asphaltene Adsorption on Alumina Surface

“…In general, petroleum porphyrins exist in homologous manifolds of several structural classes and can manifest great structural diversity. A series of papers nowadays is devoted to the determination of various vanadyl porphyrins (VP), to application of state-of-the-art massspectroscopic techniques for that purpose as well as to the development of different pathways of the effective vanadyl extraction [1,4,[16][17][18][19][20][21][22][23]. Dickie and Yen were the first to suggest that, having many of the same interactive groups as asphaltenes, petroporphyrins could also play a role in asphaltene self-assembly, adsorption, and phase separation [24].…”