NEMC 2011

In 1990, the Oil Pollution Act (OPA) was promulgated under the direction of the National Oceanic and Atmospheric Administration (NOAA) following the Exxon Valdez oil spill in March of 1989. These regulations require a Natural Resource Damage Assessment (NRDA) following a release of oil into the nation’s waterways. Currently, NOAA is conducting an NRDA to determine the impact of the Deepwater Horizon oil spill. There are several NRDA technical working groups (TWGs) assembled to determine: baseline conditions before the oil spill, the impact on plants and animals following the spill, and the current conditions of the marine ecosystem. The trustees are also evaluating impacts from the response, including the use of dispersants.

Aquatic toxicity of crude oil is critical to providing estimates of damage following a spill. Determinations of acute toxicity of crude oils require an understanding of the total composition of the source material. Measurements of the water-accommodated fractions (WAF) for semi-volatiles focus mostly on polycyclic aromatic hydrocarbons (PAHs). While this approach is effective in making chronic toxicity determinations, it falls short of measuring the initial exposure to the marine ecosystem. Less emphasis has been placed on the forensic chemistry of light distillates since the time of exposure to marine life is significantly less than middle-distillate products. Toxicity of crude oil WAFs varies with oil type and animal species tested. Results of GC-MS testing PAHs, BTEX, total volatile petroleum hydrocarbons (VPH), and total extractable petroleum hydrocarbons (EPH) found that the toxicity was greatest for PAHs and BTEX.

This presentation will address techniques for the analysis of crude oil by EPA Method 8260 purge-and-trap GC-MS to determine purging efficiencies of matrix including effects of dispersant compounds on crude recoveries and speciation of 8260 aromatics in three different sources of petroleum distillates.

Magni and Porzano described Concurrent Solvent Recondensation Large Volume Splitless Injection (CSR-LVSI) with a special low dead-volume injector, a modified septum head to reduce septum temperature, and the ability to close the septum purge during the injection (and for a period of time after the injection). They achieved excellent repeatable and linear results for injections up to 35 µL. In addition to the hardware modifications above, the principles of CSR-LVSI include fast injection with liquid band formation into a liner containing glass wool, a pre-column (e.g., 3 m x 0.53 mm) press-fitted to the analytical column, and a starting oven temperature below the boiling point of the solvent.

In the work presented here, a standard Agilent GC split/splitless injector was employed with a standard single-taper liner with wool and 0.53, 0.32, or 0.25 mm pre-columns press-fitted to 0.25 mm GC columns to achieve CSR-LVSI. In addition, the use of integrated guard columns (as retention gaps) where no press-fit is necessary was tested. No special cooling was necessary for the GC inlet septum head, and the septum purge remained open at 3 mL/min during injection and GC. Repeatable and linear results were achieved for hydrocarbons, PAHs, and other environmental contaminants with injection volumes up to 50 µL. CSR-LVSI was also employed for the analysis of EPA Method 8270 semivolatiles, reducing the need for an extended extract evaporation step.

In recent years, the advent of highly efficient liquid separations, namely ultra high performance liquid chromatography (UHPLC), and the increasing applicability of LC/MS/MS have led many laboratories to consider implementing these techniques. Most recently, the field of environmental analysis and monitoring has begun to adopt liquid chromatography. The combination of HPLC or UHPLC coupled with mass spectrometry has created a highly efficient and sensitive instrument platform capable of accurate results with high throughput. In this presentation, we will discuss the recent rise of LC and LC/MS/MS in the environmental laboratory. In detail, we will provide a technological overview, as well as a look at the recent technology trends creating applicability with environmental analysis. We will also illustrate a comparative analysis between gas and liquid chromatographic techniques. This comparison will include sample preparation needed for various matrices, chromatographic and detection comparisons, and a summary of benefits. Lastly, we will look at examples of some recent applications in LC and LC/MS/MS to define the practical usability of these techniques as they relate to the needs of an environmental laboratory.