[randoft]

HI hi...I'm going to start my final year project soon. And my project title is extraction of antioxidant and analysis using GC-MS. The control of this analysis is xanthone (antioxidant).
My supervisor ask me to find 5 type of local fruits (mangosteen is the control) to detect the presence of antioxidant (xanthone).
The questions i wan to ask is:
1) The extraction methods for each type of fruits is it similar? (cos from the internet the only method i found is the extraction from mangosteen.
2) The extraction process (solvent used) will it be influence the analysis of GC-MS?
3) Any compounds in the sample is undetectable by using GC-MS?

[JGK]

1) You will have to test the extraction method for each fruit somehow. Possibly with a Xanthone-like material not present in the fruits as an endogenous cpd

2) what is the method of analysis for the mangosteen exteact method you have?

3) I'm not sure what you mean here, what compounds (other than Xanthone) are you wanting to detect?

[randoft]

Actually i haven't start my project. So i also confused with the extraction methods for each type of fruits...The only method i found from article is the extraction of xanthone from mangosteen. The extraction method included water, ethanol and acetone... i think something like that...Can u introduce me some of the method of xanthone extraction from fruits? thank you very much...
Sorry for confusing you. the compounds i mentioned is others compound in the fruit extracts such as vitamin c (ascorbic acid), other phenolic compounds and so on, can it be detect using GC-MS?
One more question is any pretreatment process need to carry out before inject into GC-MS?
Thank you very much....
randoft

[JGK]

Performing fruit extractions is not "my field" (idid some at university trying to find Benzo(a)pyrene in avocados

Why, if you can extract xanthones from one fruit with a method would you not apply the same method to all the fruits you select.

You may need to test the efficiency of your extraction method with each fruit type but you should not need to  use a completely different method for different fruits.

As for other compounds. you may be able to detect them if your extraction method extracts these materials from the fruit also.

[randoft]

Thanks for your guide. I think i still confusing with the extraction method. The articles i read, most of the the extraction method is perform follow by HPLC separation and MS analysis. But i'm going to use GC-MS method, so i cant found any further information about the conditions of it. Any pre-treatment of extracts need to carry out before GC?
Normally what is the condition for GC separation?

 

[JGK]

That is because you did not say that your extraction method was intended for LC-MS and not GC-MS.

for GC MS i would suspect it would be best to have the final extract in a volatile (organic) solvent.

What is the liquid composition of the sample at the end of the extraction procedure you do have?

[randoft]

i haven't start my project yet. So, i can't tell you what is the composition of my extract. From your information, the extract should dissolved in the volatile (organic) solvent? If i using the tetramethylsilyly agent to the extract? Can it be possible to make it more volatile? because i read it from the wikipedia, TMS agent was normally added to make the stable compound such as alcohol, carboxylic acid and phenol more volatile. Am i right?

[JGK]

To be honest, I can't really help you any further as you don't seem to have even read the only relevant paper you have located.

If you don't know the final composition of this extract why speculate on what you need to do when in fact you may not need to do anything.  If you xanthone extract is in an organic solvent at the end of the extraction it may be perfectly suitable for GC use.

Also why use TMS, is it necessary to derivatise this compound to analyse it? The only use for applying TMS is to alkylate material and why do it if it is not necessary.