I have 7 terpene external standards but I found nearly 60 terpene compounds in my pine samples which I do not have standards. In each sample I have also internal standard. I know that between terpene volatiles the differences in chemical structure are quite diverse, not like many of the diterpene resin acids.
What is the basis to assign an equivalence to a terpene without standard using another terpene which I have its standard?
- Closest terpene with standard in the chromatogram?
- Closest terpene using chemical structure?
- Using internal standard with those I do not have external standard?
Ex. Suppose I have Pinocarvone in my sample, but not its external standard. As external standards I have a-Pinene, b-Pinene, Limonene and b-Caryophyllene. Which one could be the best for that compound and why?
This is a question addressed more to chemists than ecologists (like me).
Thank you very much in advance.
Dear Michael,
Thank you for your reply. Indeed I used a GC.MS and a GC.FID (separately) for both identification and quantification respectively. I read with a quick view the article you suggested and I found it very interesting. I will read it carefully and see what happens!!
Thank you very much!
Hi Xose, Michael,
A GCMS is perfectly able to allow both qualification AND quantification. The way you say it makes it look like a MS can't be used for quantification. In most cases quantifying with a MS using a single mass is even better because there's less change of interference with other compounds. With 60 terpenes interference could be a problem.
Quantification is not "usualy done" with standards, it's ALWAYS done with standards.
If you use another terpene for quantifiaction be ware that the respons factors might not be the same. Choose the closest chemical structure that is closest in the chromatogram. Don't use the internal standard.
Alex
Dear xose,
I think that you can have a try to use liquid Chromatograph Mass Spectrometer to analyse such diverse compouds. As far as I know, some pine trees exztracts, like diterpene acids are detected by HPLC. I always use LC-MS to analyse diterpene acids for both qualification and quantification.
Dear Chen,
I am aware about the suitability of the LC-MS to analyze diterpenes (some studies of Ken Raffa, Caterina Villari, Enrico Bonello and maybe Nadir Erbilgin). The fact is that I already analyzed them in my PhD experiment using GC-MS (for identification) and GC-FID (for quantification). I used LC-MS instead to analyze phenolic compounds. The main problem I had was that I identified more than 100 compounds and I didn't have standard for all of them, so my question was related to a possible relative quantification using chemically and structurally similar standard compounds to quantify the compounds I found in my samples. Fortunately that problem was solved, because I found some studies that used that strategy and, explained correctly, is valid for the purpose and objective of my research (is not an analytical chemistry work)
Thank you for your reply, I appreciate it.
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