Fast Petroleum Hydrocarbons Analysis for Underground Tank Monitoring

Underground storage tanks (USTs) for various petroleum-based substances such as gasoline, diesel fuel and fuel oil are monitored for leaks as authorized by the Resource Conservation and Recovery Act (RCRA). Leaking USTs (LUSTs) contaminate ground water and soil. Besides the environmental impact, there are significant financial consequences associated with fines and cleanup. UST monitoring is usually done by gas chromatography with flame ionization detection (GC–FID). Because these petrochemical samples often have a wide molecular weight range, a temperature-programmed run is required to get adequate retention of higher volatility components and subsequently elute the high molecular weight components in the same chromatographic run. The chromatographic run time of these types of samples typically takes more than 20 min. Thermo Scientific UltraFast technology makes it possible to reduce the total analysis time to less than four min. A Total Recoverable Petroleum Hydrocarbons (TRPH) analytical standard mixture is representative of the molecular weight range typically found in UST samples.

Figure 1: Top: Using UltraFast GC. Bottom: Using conventional GC.

Experimental Conditions

Thermo Scientific UltraFast TRACE GC Ultra Configuration

Column: UltraFast UFC-M1 Phase GC Column, 2.5 m × 0.1 mm × 0.4 µm

Oven: 50 °C (0.5 min hold) -340 °C (2 min hold) at 200 °C/min

Helium carrier gas at 0.5 mL/min

Results

Thermo Scientific UltraFast column technology can be used to achieve a fast analysis of a wide molecular weight range of petroleum hydrocarbons such as those found in UST monitoring. Excellent separation of a mixture of even-numbered alkanes from C₈ to C₄₀ was accomplished in less than 3.5 min. Analysis of these types of samples on a conventional GC capillary column requires > 20 min. Since temperature programming is required for this analysis, the time needed for the GC oven to cool down to the initial temperature also needs to be considered. The time required to cool down the UltraFast from 340 °C to 50 °C for this analysis is approximately 90 s, where the time required to cool down a conventional GC oven for the same temperature range is approximately 4 min, thus further decreasing the overall run-to-run time. Laboratories doing UST analysis can do approximately five times more analyses per day using UltraFast technology vs. conventional GC columns.

Conclusion

Analysis of sample containing a wide molecular weight range of hydrocarbons such as those found in Underground Storage Tanks (UST) monitoring can be done in slightly more than three min with the use of a Thermo Scientific UltraFast column. This is approximately five times faster than doing the same analysis using conventional GC capillary columns.

References

1. Underground Storage Tanks, Office of Solid Waste and Emergency Response (OSWER), U.S, EPA. http://www.epa.gov/oust/ (accessed June 12, 2012).

2. Leaking Underground Storage Tank Program Implements The Recovery Act, EPA Information Related to the American Recovery and Reinvestment Act of 2009 (Recovery Act), U.S., EPA. www.epa.gov/oust/eparecovery/ (accessed June 12, 2012).

3. Storage Tank Regulation, Florida Department of Environmental Protection. www.floridadep.org/waste/categories/tanks/ (accessed June 12, 2012).

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