Marine Science Institute, The University of Texas at Austin Overview of petroleum hydrocarbon analysis: Some insights from Deepwater Horizon oil spill Zhanfei Liu Marine Science Institute, The University of Texas at Austin Liu Lab Dr. Hernando Basosa, postdoc Meredith Evans, MS (2013-2016) Qing Wang, visiting PhD student (2015-2016) Jiqing Liu, lab technician (2015-2016) R/V Pelican February 14, 2017

How can we better understand, respond to and mitigate the threats of petroleum pollution? Species & Ecosystem Effects Environmental Remediation Petroleum Chemistry Oil Transport & Weathering Human Impacts

Chemical Composition of Crude Oil

Chemical Composition of Crude Oil 75% Aliphatic Hydrocarbons Simple Molecular Structure Relatively non-toxic

Chemical Composition of Crude Oil 15% Aromatic Hydrocarbons 75% Aliphatic Hydrocarbons Alkanes Alkenes Cycloalkanes Complex Molecular Structure High Toxicity

Chemical Composition of Crude Oil 10% Resins & Asphaltenes 15% Aromatic Hydrocarbons Polycyclic Aromatic Hydrocarbons (PAHs) Alkylated PAHs High Toxicity 75% Aliphatic Hydrocarbons Alkanes Alkenes Cycloalkanes Used to trace oil spills Low Toxicity

Petroleum Chemistry - it’s Complicated Wave action Bacterial degradation Evaporation Dissolution Sunlight O O O The unfortunate thing about petroleum chemistry, is that it’s complicated So I would argue that what we really need in order to make this less complicated is method expansion. Because… only ~25% GC-amenable Other people are doing method expansion too I’ll go over a method application we’re using O

In situ detection based on the fluorescence of oil CTD (Camilli et al., 2010, Science)

The traditional way of analyzing the chemical composition Hexane/benzene fraction; Gas Chromatography – Mass Spectrometry (16 priority EPA PAHs & Alkylated PAHs) Hexane fraction; Gas Chromatography – Flame Ionization Detector (C8 – C40 alkanes)

Gas Chromatography-Mass Spectrometry (aromatic fractions or fingerprinting) The 2014 Houston Ship Channel oil spill (Bacosa et al., 2016, Mar. Poll. Bull.)

Gas chromatography-Flame Ionization Detection Saturated hydrocarbons such as n-alkanes; TPH

Quantifying n-alkanes by GC-FID (UCM)Unresolved complex mixture

A significant amount of oxygenated hydrocarbons was formed in surface oil slicks and sandy patties after the DWH oil spill. (Aeppli et al., 2012, Environ. Sci. Technol.)

GCXGC-FID (Aeppli et al, 2014, Environ. Sci. Technol.)

Fourier transform ion cyclotron mass spectrometry (FTICR-MS) (McKenna et al., 2013, Environ. Sci. Technol.)

(Chen et al., 2016, Environ. Sci. Technol.)

Fingerprint oil source Quantify hydrocarbons This technique is fast, efficient, without pretreatment, in need of a very small sample size, and can: Fingerprint oil source Quantify hydrocarbons Provide insights into structural info of weathered oil So how did we get to this data? Is this hard to come by? Current methods, method drawbacks, expanding methods (Evans et al, Environ. Sci. Technol., in revision)

Ramped Pyrolysis – Gas Chromatography – Mass Spectrometry with Thermal Slicing Quantification Zone Cracking Zone

Thermal Slicing Py-GC-MS: Crude Oil Quantification Zone C31 C12 C13 C14 C15 C16 C17 C25 C18 C20 C19 C21 C22 C23 C24 C30 C26 C27 C28 C29 C32 C33 Now that you’ve seen how this technique works, I want to walk you though how we can apply it to simplify petroleum weathering, using samples we’ve collected from the DWH spill. Cracking isn’t seen until the 5th range, so we can use these slices for quantification. *5.5 minute peak = internal standard

337 d Tar - High Temperature Thermal Slicing Py-GC-MS: Structure Zone 337 d Tar - High Temperature Structure Zone Now that you’ve seen how this technique works, I want to walk you though how we can apply it to simplify petroleum weathering, using samples we’ve collected from the DWH spill. Cracking isn’t seen until the 5th range, so we can use these slices for quantification.

Detected n-alkanes and aromatics in the cracking zone (370-650C) (Evans et al., EST, in revision)

The new Agilent HPLC-ion mobility (IM)-Quadrupole-Time-of-Flight system (ERC 3rd floor)

(From Agilent)

Take home message A further understanding of the oil spill in marine environments relies on the development of analytical instruments. From the Deepwater Horizon oil spill, both ultrahigh resolution MS and pyrolysis GC-MS showed promise in deciphering structures of petroleum hydrocarbons.