Chromatography Forum

I need some help setting up an oil range calibration. The state requires TEPH DRO as C11-C28 and is about to request adding on TRPH C29-C35 which I guess to be motor oil or maybe hydraulic oil. Up till now I have not needed to quantitate motor oil. What is a good motor oil brand and weight to go with for the C29-C35 range?

I have an SAE 30W Motor oil standard that I am going to dilute and run tomorrow.
AccuStandard FU-018-H-40X 20mg/mL in hexane

For DRO, I'm currently shooting 5uL per shot so my MDL is 25 ppm and max cal is 50,000 ppm. I'm thinking I should make the ORO calibration separately and then run either calibration separately for reporting. This because mixed sample types have overlap between the DRO and ORO ranges. How is this overlap typically handled? Any suggestions would be welcome.

UPDATE:
I have tried these non-detergent oils...
3-in-1 20W, Penzoil 30W, Napa 30W, and Mag1 30W Lubrication Oil.

All of them have a range similar but more mashed out in appearance than the AccuStandard above. I used the Penzoil 30W to make an 8-level calibration curve from 10,000 ppm down to 50 ppm. (10K, 5K, 2.5K, 1K, 500, 250, 125, 50) The fit was excellent and reproducible.
Checking with a 1000 ppm standard made from a 20X dilution of a new 20,000 ppm AccuStandard reads as 3000 ppm. So, somehow the AccuStandard is more volatile than the Penzoil 30W seems to be. Note that all these motor oils are supposed to be non-detergent straight 30W.

In my past life, I'd run a solvent blank for baseline, then an aliphatic RT marker standard (NJDEP EPH from restek is c9-c40) to define my carbon ranges. DRO Range is Right before your C11 and right after your C28 elutes, and past that until after c40 elutes is oil range (in your case, just stop it after C35 elutes). Then I run a diesel#2/motor oil composite as the calibration curve (restek makes one of these too). Use the solvent blank as a baseline reference for the motor oil range if you have column bleed. Although the carbon ranges of standards overlap, you're still only measuring what's within that retention time window, so I don't see a need to run two calibrations. The only pain of this is making sure your diesel range and oil range integrations line up with each other, in my opinion.

https://www.accustandard.com/prod0049689.html

We would use a combo standard with diesel and motor oil from a reputable source. however, you could certainly make your own; just stick to the same product each time.

I second the use of a RT marker, any n-hydrocarbon standard or CT ETPH n-hydrocarbon standard would work well.

In my past life.....

Are you Shirley Maclaine?