Chromatography Forum

Hi all,

we have some problems with a oily sample matrix.
Does anybody has some suggestions/recommendations for dealing with such samples?

Thank you.

My first suggestion is that you supply some more information; what kind of oil is it, animal, vegetable, or mineral ?

What are your analytes, at what concentration ?.

What detector, column and mobile phase are you using ?

Peter

Depends a lot in what ypu are looking for...

There are hundreds of methods for sample prep and there must be something for you...

Yes, depends on what you are looking at. Many times we need to remove oils from matrix and the first thing I typically try is a acetonitrile hexane back partition. Works great if your analyte partitions into the ACN. All oils will partition into the hexane fraction. However, if your analyte is extremly non-polar and partitions into the hexane, it is obviously useless.

Using LLE is not a good idea to separate oily matrix since oily based formulation (drug, creams, ect) always contains some surfcants which troubles the water-oil phase separation.

try to do a literature research on matrix solid phase dispersion (MSPD), this technology is very useful in extracting desired analyte from oily matrix, such as tropical cream, oils, oil-based cosmetics, etc. I have used it a lot when I was in graduate school. Good Luck

I have had good luck with liquid-liquid extraction for steroids in ointment formulations. Disperse the sample in ethanol:heptane, then add water and centrifuge. This trick works for a variety of semipolar analytes.

I've extracted many pesticles from matrices containing oils such as nuts (pecans, almonds) and you must get the oil out of extracts. The method usually entails rotory evaporating the organic extract down to the oily residues followed by reconstituting them in hexane. Transfer hexane fraction to sep funnel add equal volume ACN shake and partition. Bingo, 98% of the time your analyte is now in ACN and your oil is in the hexane fraction headed for the non-halogenated waste container.
But like I said, what are you looking at? If what you want to look at partitions into the hexane I would not suggest this methodology.

We had good results analysing APIs in "suitable vegetable Oil" by NP LC. There are other tricks to use, but that depends o your application.

Alex