Characterization of Naphthenic Acid Singly Charged Noncovalent Dimers and Their Dependence on the Accumulation Time within a Hexapole in Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Naphthenic acids are believed to be responsible for a number of unwanted phenomena occurring during the processing and transport of crude oil, such as pipeline corrosion and precipitation of calcium salts. In this paper, Fourier transform ion cyclotron resonance mass spectrometry is used to analyze a mixture of naphthenic acids. Naphthenic acids have been shown to form multimers, and the study of multimer association could lead to a better understanding of naphthenic acid phase behavior in crude oil production systems. The dependence of the signal intensity of such aggregates on the accumulation time within the ion source hexapole has been studied, and it has been highlighted that such a dependence suggests a noncovalent interaction as the primary cause for aggregation. This would account for the decrease in signal intensity with accumulation time as a result of the increasing chance of undergoing collisional dissociation. The nature, role and behaviour of naphthenic acid dimers may be better understood by the application of mass spectrometry and this has potential to be applied to samples of importance to the oil industry.