Method Development for Quantitative Analysis of Polycyclic Aromatic Hydrocarbons, Nitrogen Heterocycles and Sulfur Heterocycles in Crude Oils Using Quadrupole Time-of-Flight Mass Spectrometry

Abstract

An oil spill is a catastrophic event that results in various toxic polycyclic aromatic hydrocarbons (PAHs) entering the environment. Polycyclic aromatic nitrogen heterocycles (PANHs) are more toxic to the environment than their parent PAHs. The high cost and paucity of available PANH standards, the lower abundance of PANHs relative to PAHs, and the difficult separation due to co-elution with PAHs have all contributed to the scarcity of related published literature on the determination of these compounds. To overcome these challenges, a new quantitative method has been successfully developed and validated for the inclusion of 113 polycyclic aromatic carbon (PAC) compounds in a single injection. The 113 compounds consist of PAHs, nitrogen heterocycles, sulfur heterocycles, and alkylated equivalents. Distinct separation of the PANHs and their alkylated counterparts (APANHs) from PAHs was achieved using a gas chromatography quadrupole time-of-flight (GC-QToF) mass spectrometer. The instrument resolved compounds by the high-resolution extraction of monoisotopic masses, allowing response correction factors (RCFs) to be determined from available PANH standards and to calculate concentrations from PAH calibration standards. The developed method was applicable to crude oil samples, generating concentrations of PANHs and relevant information on compound stability for use in oil spill forensics investigation. Development of this practical PAC method provides a powerful tool for screening toxic contaminants, assessing environmental impact, and monitoring recovery following an oil spill.