For one of many possible reasons (e.g., regulatory requirement, environmental spill, property sale) you submitted samples to your laboratory for diesel range organics (DRO) analysis. Upon receiving the laboratory report, you discover you have positive DRO results reported where you did not expect that your samples contained diesel fuel.
Take a deep breath after your instinctive “oh no.” Something to consider prior to pondering the remedial dollar signs is that there is one very common misconception about DRO. A positive result for DRO does NOT automatically mean that diesel fuel is present. While diesel fuel will be reported as DRO, a DRO positive result does not necessarily mean your sample contains diesel fuel. The same is true of gasoline range organics (GRO) and gasoline; however, I will focus on DRO today.
It is all in the name. Diesel range organics is an operation definition of any synthetic and/or naturally occurring organic compound that happens to be in the same boiling point range as diesel fuel. In other words, while a positive result for DRO might very well mean you have diesel fuel present in your samples, it could also mean that you have any number of synthetic and/or naturally occurring organic compounds present. When a laboratory reports DRO, it necessarily means that the responses of all gas chromatographic (GC) peaks that elute within the method-defined carbon range of diesel are all summed and reported. Unless your regulation(s) defined a specific method or carbon range, the routine boiling point range used by the laboratory would encompass C10 through C28, as defined in SW-846 Method 8015C. Notwithstanding the Federal US EPA method, there are approximately 20 states that have adopted state-specific methods for DRO analysis. The common thread with all of these methods is a positive result for DRO does not necessarily mean you have diesel fuel in your samples.
Samples collected for DRO analysis are extracted in an organic solvent, routinely methylene chloride, and then analyzed on a GC equipped with a flame ionization detector (FID). Since the FID used to analyze samples is a non-selective detector, many non-diesel fuel compounds present in a sample will be counted as DRO. Many naturally occurring biogenic materials as well as pure synthetic compounds such as phthalate esters (viz., plasticizers) will be reported as DRO.
Since this is such a subjective, operationally defined test, close evaluation of the chromatographic data by chemistry subject matter experts is necessary prior to acting (e.g., $$$) on positive results. This is where my team can help. In addition to independent third-party data validation, we have senior chemistry personnel experienced in evaluation of the gas chromatograms. Data evaluation by a senior chemist can help determine:
- If the sample is diesel fuel or some other hydrocarbon, since even a single peak will be reported as DRO.
- Potential ownership of the product if a source sample was analyzed.
- Comparison to patterns from other on-site or off-site samples.
- How old the product may be.
- If the results are biased due to additional interferences present in the sample.
If you contact our team first, we can help develop an analysis plan specific to the analysis of diesel fuel and tailored to the information you actually need for your important liability and business decisions.