Time-of-Flight Mass Spectrometric Analysis of High-Molecular-Weight Alkanes in Crude Oil by Silver Nitrate Chemical Ionization after Laser Desorption

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Abstract
Time-of-flight mass spectrometry was used for the first time to analyze the hydrocarbons in crude oil. Alkanes in the saturated fraction of a crude oil sample were chemically ionized by the laser desorption of silver nitrate, and the silver-attached C24−C60 alkanes were resolved with mass accuracy below 7 ppm. This technique was used to evaluate the biodegradation of aliphatic hydrocarbons and cycloalkanes by oil-degrading microorganisms resident in seawater. It is shown that the aliphatic hydrocarbons were degraded in the range of 60−80%, while the mono-, di-, tri-, tetra-, and pentacycloalkanes were degraded in the range of 40−55, 20−30, 10−16, 5−9, and <5%, respectively. Its high sensitivity and speed of application could result in an analysis by laser desorption silver chemical ionization time-of-flight mass spectrometry being the method of choice for determining high-molecular-weight hydrocarbons in various petroleum products.