For decades, discussion of asphaltene structure focused primarily on molecular weight. Now that it is widely accepted that asphaltene monomers are between ∼250 and 1200 g/mol, disagreement has turned to asphaltene architecture. The classic island model depicts asphaltenes as single core aromatic molecules with peripheral alkyl side chains, whereas the less widely accepted archipelago model, includes multiple aromatic cores that are alkyl-bridged with multiple polar functionalities. Here, we analyze asphaltene samples by positive-ion atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry and perform infrared multiphoton dissociation to identify their aromatic core structures to shed light on the abundance of island and archipelago structural motifs. Our results indicate that island and archipelago motifs coexist in petroleum asphaltenes, and unlike readily accessible island motifs, asphaltene purification is required to detect and characterize archipelago species by mass spectrometry. Moreover, we demonstrate that mass spectrometry analysis of asphaltenic samples is biased toward the preferential ionization/detection of island structural motifs and that this bias explains the overwhelming mass spectral support of the island model. We demonstrate that the asphaltene structure is a continuum of island and archipelago motifs and hypothesize that the dominant structure (island or archipelago) depends upon the asphaltene sample.

中文翻译：

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沥青质石油化学的进展。第1部分：沥青质由丰富的岛和群岛结构母体组成

几十年来，关于沥青质结构的讨论主要集中在分子量上。现在，人们普遍认为沥青质单体的含量在约250至1200 g / mol之间，争论已转向沥青质结构。经典的岛模型将沥青质描述为具有外围烷基侧链的单核芳族分子，而较少被接受的群岛模型包括多个被烷基桥连且具有多种极性官能团的芳香族核。在这里，我们通过正离子大气压光电离傅立叶变换离子回旋共振质谱分析沥青质样品，并进行红外多光子离解，以识别其芳香核结构，以阐明岛上和群岛上的大量结构图案。我们的结果表明，岛屿和群岛图案共存于石油沥青质中，并且与易于获取的岛屿图案不同，需要通过沥青质纯化来检测和表征群岛物种。此外，我们证明了沥青质样品的质谱分析偏向于优先电离/检测岛结构图案，并且该偏倚解释了岛模型的压倒性质谱支持。我们证明沥青质结构是岛和群岛图案的连续体，并假设主要结构（岛屿或群岛）取决于沥青质样品。需要通过沥青质纯化来检测和表征群岛物种。此外，我们证明了沥青质样品的质谱分析偏向于优先电离/检测岛结构图案，并且该偏倚解释了岛模型的压倒性质谱支持。我们证明沥青质结构是岛和群岛图案的连续体，并假设主要结构（岛屿或群岛）取决于沥青质样品。需要通过沥青质纯化来检测和表征群岛物种。此外，我们证明了沥青质样品的质谱分析偏向于优先电离/检测岛结构图案，并且该偏倚解释了岛模型的压倒性质谱支持。我们证明沥青质结构是岛和群岛图案的连续体，并假设主要结构（岛屿或群岛）取决于沥青质样品。