Crude oil plays a vital role in all aspects of life. A raw hydrocarbon resource, it not only powers our vehicles but can also be used to fully assemble them. Gathering this resource requires extensive drilling and refining operations, and few places illustrate this better than Texas, which produces close to 25% of the USA supply. Monitoring areas where petroleum is drilled, refined, transported and stored is critical to preserving water and soil quality. To support monitoring, the Texas Commission on Environmental Quality (TCEQ) (formerly known as the Texas Natural Resource Conservation Commission (TNRCC)) developed TNRCC 10062, commonly known as TX 1006, to quantify total petroleum hydrocarbons (TPH) in environmental samples. In this blog, we will discuss the TX 1006 method and how it is utilized for assessing areas in which hazardous petroleum hydrocarbons may enter our environment.
Proper sampling and storage are essential to ensuring the highest level of sample integrity prior to analysis. Soil and water samples should be treated differently, as highlighted in Table 1. Sample holding times vary by matrix and preservation conditions, with extraction required within the method-specified timeframes and extracts analyzed within 14 days of extraction.
Table 1: TX 1006 sampling parameters*
|
Matrix |
Container |
Preservation |
Holding Time |
|
Aqueous |
1-Liter amber glass bottle with Teflon-lined screw cap |
pH<2 with sodium bisulfate, hydrochloric acid or sulfuric acid; Cool to 4 ± 2° C |
Samples must be extracted within 14 days (7 days for unpreserved) and extracts analyzed within 14 days |
|
Soil/Sediment |
10g; Tared 40 mL VOA vial with a PTFE-lined septum cap |
Cool to 4 ± 2° C |
Samples must be extracted within 2 days and extracts analyzed within 14 days of extraction |
|
10g; Tared 40 mL VOA vial with a PTFE-lined septum cap |
Freeze at - 15°C in the laboratory. |
Samples must be extracted within 14 days of the date thawed and extracts analyzed within 14 days of extraction. |
*Parameters taken from TNRCC 1005
To fully understand the scope of TX 1006, it’s important to note that it runs in conjunction with TNRCC 10051. In TNRCC 1005, soil and water samples undergo a pentane extraction to measure their total petroleum hydrocarbon (TPH) concentration. The TPH range for this method is defined as aliphatic and aromatic hydrocarbons ranging from six (C6) to thirty-five (C35) carbon atoms. To further classify the types of hydrocarbons that are found within this range, the pentane extract undergoes solid phase extraction (SPE) with silica to separate the aliphatic and aromatic hydrocarbons. TX 1006 is a specific method that covers the fractionation portion of samples extracted under TNRCC 1005 for TPH. After the pentane extract passes through the silica, the long-chained aliphatics are eluted with additional pentane, and cyclic aromatics with dichloromethane. The aliphatic hydrocarbons range from C6 to C35, while aromatics are identified as hydrocarbons within C7 to C35, with reporting typically beginning at the C8 to C10 range. This means compounds such as benzene and toluene are not included in the reported results. The fractions are then concentrated separately under ambient nitrogen conditions before being injected onto the GC-FID for analysis.
Unlike EPA methods, TX 1006 was developed by a state agency, making it more specific to Texas regulations. A practical example where TX 1006 could be used is evaluating soil samples from a potential oil leakage of an underground storage tank. Soil and water samples from nearby streams or creeks could be collected and analyzed for petroleum presence. Results are reported as a single value across the hydrocarbon ranges instead of individual values for each hydrocarbon. In other words, TX 1006 indicates whether petroleum contamination is present, but does not identify individual contaminants, making it an ideal screening method. This is particularly important when we consider whether any remediation efforts need to take place. If it is necessary to look further into individual hydrocarbon concentrations, there are more specialized options available, such as EPA 8270, which measures polyaromatic hydrocarbons (PAH) in crude oil. This distinction lets clients determine if they need further analysis, saving laboratory and testing resources in the process.
The manual steps involved in TX 1006 fractionation, including pentane extraction, silica SPE cleanup, and solvent evaporation, are well-suited to automation. When laboratories are processing large sample batches, these steps can become time-consuming and introduce variability between analysts.
Automating the SPE workflow can help standardize fractionation, improve reproducibility, and reduce hands-on sample preparation time. Automated systems can perform cartridge conditioning, sample loading, washing, elution, and fraction collection with a high degree of consistency, while automated evaporation systems can support extract concentration prior to analysis.
Biotage® Extrahera™ and Biotage® PRESSURE+ can be integrated into this workflow to streamline SPE fractionation and extract concentration, allowing laboratories to increase throughput while maintaining consistent sample processing.
Petroleum products and their environmental impact are ingrained into the daily lives of people and wildlife alike. Both rely on clean water and soil to fully function and thrive. As we continue to depend on crude oil, we must be responsible for protecting the planet’s resources in the process. TX 1006 was created to address those concerns, providing a straightforward screening tool for assessing petroleum contamination in environmental samples. By helping laboratories distinguish between aliphatic and aromatic hydrocarbon fractions, the method supports informed decisions regarding further testing, investigation, and remediation efforts.
Learn more about SPE-based fractionation and cleanup workflows for petroleum hydrocarbons in environmental samples.
Sources: