Diesel Contaminated Motor Oil
In a previous blog post we ran diesel contaminated oil with great success without the need for backflushing. Afterward we were contacted by labs that do this type of testing and they asked if we could use Heptane as a wash solvent rather than Dichloromethane. The reason was that they already had a waste stream for hydrocarbons but not for halogens.
It seemed easily enough to change out what wash solvent is used, so I dove in and began testing with Heptane.
As before, I ran the following parameters for the Lucidity GC-FID.
| Lucidity GC-FID Conditions | |||
|---|---|---|---|
| Carrier | Hydrogen | ||
| Control | Pressure | ||
| Flow | 1.0 mL/min | ||
| Split ratio | 100:1 | ||
| Column | Rtx-1 | 30 m x 0.25 mm, 0.25 um | |
| Injector | 300 ℃ | ||
| FID | 325 ℃ | ||
| Oven Program | |||
| Rate | Temperature | Hold Time | |
| 225 ℃ | 3 min | ||
The samples used for this study were the same samples from the previous study. To recap, there are the 4 standards and 1 check standard in mineral oil, as well as 6 motor oil samples with varying amounts of diesel contamination.
A 5% Diesel in Oil standard
Oil sample with no contamination
These chromatograms show that the results are extremely similar to the previous study, but the purpose of this study was not to compare these results to previous results, it is to see if Heptane cleans as well as Dichloromethane.
After the samples were finished I changed out the septum and liner, both of which had oil contamination visible on them. Once the consumables were changed I ran a blank that injected nothing.
A no inject chromatogram showing a small peak
Second blank showing no contamination
As you can see the first blank had a small peak, but that peak isn’t at the retention time of oil. But, on the second chromatogram is completely blank, there are no peaks at all, showing that the Lucidity GC-FID can run ASTM method 7593 without the backflush and with Heptane as the wash solvent.