Recently we became aware of an interesting and very popular GC-FID application. Users of heavy machinery regularly send out samples of their engine oil to monitor the performance and status of their machinery, and there are specialty labs all over that specialize in the testing of this oil via GC-FID.
With Gulf Coast Conference 2024 coming up, we set out to find a company that uses heavy machinery that sends their engine oil in for testing and ask them why they send in their engine oil every month. We found a logging contractor, Select Timber, Inc.
Select Timber, Inc. a local NC production logging contractor and timber buying company worked diligently with Lucidity to support this application. Select Timber, Inc. President Zack Myers provided oil samples to Lucidity for testing on the Lucidity GC-FID. Testing oil for diesel contamination is a common practice for their machinery. Upon servicing, Myers sends samples out for third-party lab testing to ensure the integrity of their field instruments, such as loaders, cutters, skidders, and road tractors. “I make sure we take all precautions to know the status of our equipment. Testing the oil samples keeps the equipment safe and gives me peace of mind that my investments are functioning properly”, says Myers. A huge thanks to Select Timber, Inc. for working with Lucidity on this application.
The heavy machinery manufacturers use a standard method to analyze for the contamination of diesel fuel in the oil, ASTM D7593. This ensures that all seals are in good working order and that the engine is either failing or operating as intended. The sooner an issue can be spotted the sooner it can be addressed. It also is required to keep the manufacturers warranty intact. This method is outlined below:
| 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 | ||
We then took some samples of the engine oil and began to test the oils for diesel fuel contamination.
I began by making a standards by diluting diesel fuel in mineral oil, making a 10%, 5%, 3% and 1% standards. A check standard was made at 6% to ensure that the standard curve was accurate.
Chromatogram overlay of the diesel standards
As you can see the overlay shows that all four standards overlay nicely on top of each other. Next, was to create the calibration curve from the data.
Calibration curve of diesel fuel
As you can see the 5% standard was just a bit low but the overall R squared value was 0.99 so I decided to continue with the experiment.
Chromatogram of the 6% check standard
The check standard was run next and the value calculated to ensure that the calibration curve was accurate. With a total area of 478.26 of the diesel blob, the concentration of the check standard was calculated to be 5.7%, fairly close to the expected value. Next were the samples to see if there was any contamination in the engine oil.
In total there were 6 samples run with a blank at the end to see if there was any carryover of the oils from one injection to the next.
Chromatogram of sample 1
The first sample here shows a clean baseline and no contamination of diesel fuel in this oil and the engine would be given a go ahead to keep running.
Chromatogram of sample 2 showing major contamination
Sample 2 shows major contamination of diesel and other components and this engine should be removed from used until the source of contamination is determined and fixed.
Chromatogram of sample 3 showing slight contamination
The third sample shown here has slight contamination and would need to have the oil sampled again to check these results.
After the runs a blank of dichloromethane was run.
Chromatogram Showing a Clean DCM Blank
Then a bake out was performed to ensure the Lucidity GC-FID was clean. There was a bit of contamination and the consumable injection count was checked. There had been 90 different oil injections done on the liner and septum. These consumables were changed and another bake out performed.
Chromatogram of a Clean Bake out
As you can see after changing out all of the consumables the Lucidity GC-FID is back to a clean stable baseline and ready to run more analysis. This offers a major advantage over conventional systems where a special valve setup is used to backflush the column to remove contaminants between runs. In the Lucidity GC-FID, we are able to run ASTM method 7593 without the backflush.