Chromatography Forum

Hi,

I ran across a GC-MS report as seen below:
https://ibb.co/ftBd6U

The tester concluded the essential oil was adulterated due to the low TIC count.
How could one estimate the level of dilution just from the resulting report?
I read up and understand that a quantitative analysis could have been done, with the use of an internal standard in a known concentration, or better perhaps with a curve of an IS in various concentrations.
How does one assess non volatile content in a GC-MS?


thanks for the help

My guess is they're assuming it was cut with something non-volatile because they don't see the adulterant on the scan (except for the phthalates). TIC simply refers to the peak area when you're not running in SIM-mode or looking at a specific ion. So what they're saying is that if this were unadulterated the peaks associated with Agarwood essential oil would be bigger. If they're doing headspace analysis, non-volatile additions like sugars or other organics can reduce volatility of organic compounds, resulting in lower concentrations in the headspace and since they're non-volatile they won't show up in the chromatogram themselves.

However I don't know that this is the best way to detect adulterants. Without the QC such as an internal standard like you mentioned and/or a calibration curve, it's hard to say definitively if the low TIC is due to the sample or due to the instrument/method. With this report alone, it would be difficult to estimate the amount of dilution/adulteration with any sort of rigor. I have seen papers where people have used ion suppression as a sign of adulteration (using cachaca to dilute scotch, for example) and they basically made a calibration curve using different levels of adulteration (from pure scotch all the way to pure rum).

Hope that helps

Thank you very much for the reply, I did find it useful.

>>If they're doing headspace analysis, non-volatile additions like sugars or other organics can reduce volatility of organic compounds, resulting in lower concentrations in the headspace and since they're non-volatile they won't show up in the chromatogram themselves.

Sorry I took my time to reply,
I was pretty sure headspace analysis was not used, but I wanted to see if I could ascertain the actual method.
The essential oil was injected with a solvent, methylene chloride.


>>using cachaca to dilute scotch

Hmm, such adulteration didn't even cross my mind....
pfff, is anything pure anymore...?
something like this?
https://www.researchgate.net/publicatio ... ectrometry

thanks