GC-MS analysis of total petroleum hydrocarbons and polycyclic aromatic hydrocarbons in seawater samples after the North Cape oil spill

Abstract

We developed a gas chromatograph-mass spectrometer (GC-MS) method for measuring both total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs) in seawater samples that were collected after the North Cape oil spill. After the samples are extracted with methylene chloride and hexane, the extracts are fractionated on silica-gel columns and then injected into a GC-MS operating in the selected-ion-monitoring (SIM) mode. The signal from the ion m/z 57 (C 4H 9 +), which is a major ion in aliphatic compounds, is integrated throughout the chromatogram and used to calculate the amount of TPHs. The PAHs are analyzed by using distinct quantification ions during the same run. This method is faster than conventional gas chromatography techniques that use both flame ionization detectors for aliphatics and mass spectrometers for PAHs and also gives a more positive identification due to using GC-MS. Laboratory blanks, recoveries from spiked seawater, and method detection limits for TPHs and PAHs with the simplified method are comparable to conventional methods. Over 50 seawater samples were analyzed after the North Cape oil spill, and the concentrations of TPHs and total PAHs were as high as 3940 and 115 μg 1 −1, respectively.