GC or GC-MS

[dave]

Hi all, hope all is well.

i was wondering if someone could shed some light on a topic for me please.
is "GC-FID" sufficient enough in terms of quality control of essential oils. I have seen a lot of work has been done using GC-MS, however its not a kit i have or can afford just yet!!!

would appreciate any information available or pointer in the right direction.

Thanks again

[willnatalie]

What kind of oils?
If much of the oil needs to be identified, then an MS would be much easier as there could be many compounds present.
If its something where an ASTM method can be used or only a few specific compounds need to be verified and quantified I believe an FID could work. An more non-polar column such as 100% dimethylpolysiloxane column, or 5% Phenyl dimethylpolysiloxane could be used for separation.
I think it will simply depend on how much of the sample needs to be identified and/or the number of compounds in the specific oils.

hope this helps


Good Luck.

[Don_Hilton]

Even with GC/MS, using chromatography for qc can be tricky. If you are compunding mixtures including previously QCed oils - GC-FID is fine.

For QC, the question is what criterion are you trying to meet? Good aroma is best determined by trained noses. And, thre are techniques for this type of QC work.

The problem with GC or GC/MS in looking for failed product is that you have to know what to look for to see if it is there or not. In oils there often are many peaks other than the key components to the fragrance - and the size of these peaks can vary quite a bit with little or no effect on the qualtiy of the aroma. Then, there are a few compunds which, if present, will give an off note at phenominally low conentration - such that you may not see the small chromatographic peak in the forest of other compounds.

If the QC is analysis for pesticides, you will need GC/MS.

[dave]

Thanks guys, appreciate the response, it sounds like even with GC-MS it can still be a tricky analysis!

I am still awaiting more information as to what kind of oils will be sent, how much of it needs and what compounds will need to be identified. Main discussion has be around the subject of purity and the level of organics in the oil.

While I was waiting for more information I thought i'd try my hands at the GC part just to get an idea of running the oils on GC and see what kind of results I get. And if I can start some kind of data base, to get some kind of head start.

I found an application by Agilent that i thought of using, it uses GC-FID then using GC-MS, using "retention time locked method and retention time databases". I am thinking of trying this out with just the GC-FID to see what kind of results i get.

If you are aware of this method or have used it, again i would appreciate any feed back you can give me.

Thanks again

[Don_Hilton]

Noting that part of your discussion has been about the level of organics in the oil: essential oils are close to 100% organic compunds - if you are speakign as a chemist. If you are talking about organic as from sources that do not use industrially produced materials in growing the plants from which the essential oils are extracted, that is a different matter entirely - and not necesarily easily provable by chemical analysis of the oils.

The Agilent retention time locking is a way to make use of retention time indicies for matching compounds from run to run. Agelent adjusts column flow to keep compounts at a given retention index eluting at a specific time in the run. If you have the software and instrument control, give it a shot. If you do not have the package for doing this, retention time checks on a paraffin solution and computation of retention indicies for the peaks in the essential oil runs can get you the same information. Depending on the data system, it may be a bit more work.

[WK]

Hi Dave,
You will need to consider which polarity columns to use. Most column manufacturers will have application chromatograms for essential oils -
less polar columns for citrus oils and more polar columns for mint oils and some fragrance type oils. Care needs to be taken to resolve the components of interest - slowest temperature ramps aren't always the "best".
Let the forum know how it goes if possible.
WK
Sorry - this agrees with willnatalie's post