Chromatography Forum

Hi everyone. I need to quantitate mineral oil (liquid vaseline) as an API in our pharmaceutical product. It is a water based solution with preservatives, essences, thickeners, etc. I thought this could be done by GC-FID analysis, but I´m not sure. I have my doubts on how to quantitate and express my results, because I think it will have lots of peaks and how to use a standard? Same API with a calibration curve? Is it necessary to do SPE or extraction with organic, eg n-Hexane? Don´t think injecting directly because of excipients may damage GC.
Does anyone known any literature or ideas to put me in the game?

That's actually a great question, and I've given it much thought over the years, for mineral oil, petrolatum, and other OTC actives.

If you can get mineral oil to elute on a high-temperature column and do by area summation, you still need to have a "stability indicating" assay, and who says that a reference standard would have similar distribution as your active?

Yet I see mineral oil, petrolatum listed as Drug Actives in the US Drug Facts boxes. I doubt that folks are simply extracting and quantitating gravimetrically, that's tough to justify as stability indicating for stability studies.

Hi

Indeed, as CPG says, an interesting 3 pipe problem.

Mineral oils should have a lower bp range than petrolatum and the range will depend on the SUS rating.

Below is a chromatogram that I obtained from a beauty cream. It is not a great deal of help because it was an SPME headspace analysis but it shows how horrible a mineral oil trace is due to the high proportion of branched hydrocarbons.

I would suggest trying a hexane extraction and see what you get. If the mineral oil is the main API the excipients may not contribute too much if they co-elute. And yes try a calibration curve with the same API or a standard addition


http://tinypic.com/view.php?pic=11r7hus&s=9

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Regards

Ralph

For quantitation you could take the Arochlor approach; sum all the oil peak areas, or integrate across the bottom of the spikey hump, and calibrate with known hydrocarbons of similar MW.

Peter

Years ago I had to quantitate the amount of punch-press lubricant in some bottle caps. Similar situation - not a single component and actually a distribution of materials like your petrolatum. I did what Peter describes. I used standard addition to calibrate and the actual lubricant as the standard. It worked well for my purposes. My analysis was not regulated or reportable to any type of government agency, however.

Thank you all. I will see what can I do. Costa Rica government health department is giving me a headache.