Optimizing detection limits for the analysis of petroleum hydrocarbons in complex environmental samples

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Ecotoxicology

Background:

• Environmental studies require accurate quantification of hydrocarbons like polycyclic aromatic hydrocarbons (PAH), alkanes, and biomarkers to assess spills.
• High method detection limits (MDLs) can lead to misidentification of hydrocarbon sources, impacting ecological risk assessments.

Purpose of the Study:

• To improve the accuracy of hydrocarbon analysis in environmental samples by lowering MDLs.
• To enhance the resolution and quantification of hydrocarbons from multiple sources.
• To refine analytical methods for better ecological risk assessment.

Main Methods:

• Modifying U.S. Environmental Protection Agency Method 8270 to lower MDLs.
• Utilizing gas chromatography-mass spectrometry (GCMS) in selected-ion-monitoring (SIM) mode.
• Increasing sample size, performing column cleanup, and decreasing preinjection volume.
• Developing a method to estimate MDLs for compounds lacking commercial standards.

Main Results:

• MDLs were reduced by factors of 10 to 1000.
• Achieved MDLs below 0.5 ng/g (ppb) for individual PAH and biomarkers, and below 5 ppb for alkanes in spiked sediment samples.
• Successfully identified and quantified low-level hydrocarbons from natural and anthropogenic sources in Prince William Sound sediments.

Conclusions:

• Lowering MDLs through modified analytical techniques significantly enhances the ability to identify and quantify hydrocarbon sources.
• These improved methods are critical for accurate environmental monitoring and ecological risk assessment of petroleum-contaminated sites.
• The developed methods allow for the characterization of complex hydrocarbon mixtures in environmental matrices.