i wish this article can help you , there you can find conditions used for GCMS .

Article In vitro Antibacterial Activity of Essentials Oils from Ment...

Hi Surendra

Many things may affect the constituents present in the oil. Your source and the source used in the paper you are following must be different and hence the composition is different. The climatic conditions in which that plant was grown will be different from yours. When you know it is Marigold, just try to find the components present in Marigold according to literature. This is what is called as a fingerprint. Every plant or phytochemical compound has a unique fingerprint which differs from the other one and it is affected by environmental and experimental factors, which may be the cause in your case too. 

Why don't you use the corolla portion which may be having other compounds? Only sepals and leaves may have lesser compounds. Hopefully this might be the cause of major differences from the published literature. Mostly essential oil is extracted from the petals when using flowers as the source. Try to do this also and revert with the result. This is interesting and this is what is referred to as 'Variability in Drug Activity'.

Regards 

Ohh..thanks Alokji...for the information you have given.....and explaining about the phenomenons.....actually in Marigold if u can see there wont be any perfumery in the petals...it mostly concentrated in the calyx/disc portion....(take a fresh flower, open the seed portion (green calyx below petals) and smell it you will have a distinct aroma at the same portion)...so using petals will be futile i hope....I am following a literature from Iran (attachment) and the same condition are being used for GCMS....but not getting atleast a single compound matching...this is something disturbing to me....according to the literature...most of the leaf and calyx GCMS components are matching...which I am failed to get.....Thank you very much Alokji...please see the attachment....the other attachment is another reference.....

try the super State technical critics

Super State technical critics, I didnt get them Mr. Beth...can you explain it?

apply the technique of supercritical fluid. Supercritical fluids are produced by the heating of a gas above its critical temperature or compression of fluid above its critical pressure. The critical temperature of a substance is the temperature above which the liquid phase cannot exist, regardless of pressure. The vapor pressure of a substance in its critical temperature is its critical pressure. Pressures and temperatures above but close to its temperature and pressure critical (critical point), a substance is known as a supercritical fluid. Carbon dioxide is the most used by its low critical temperature (31° C) supercritical fluid, be inert to be of low toxicity and reactivity and high purity low-cost.

I do not understand why, after extraction of the e.o., you trat it with hexane/petroleum ether in a separating funnel and then you concentrate at the rotatory evaporator. During this procedure, in particular during concentration, you may lose the most volatile compounds. Have you tried to prepare a solution of the e.o. directly in hexane (about 10%) and inject it directly in GC-MS?

yes Mr. Guido....as I mentioned at the last...of the original question.....I took some 50 g of leaves chopped and treated with hexane directly in the Clavengers apparatus, collected the condensed hexane (with oil content)...and finally concentrated with rotatory evaporator....still was not getting the compounds.....Dont know the mistake I am doing

Sorry, but I have not understood your procedure. Do you extract the leaves in the clevenger apparatus using hexane hexane instead of water? Or something different? Please, clarify and I try to give some suggestions

Yes Dr. Guido....In one process I used only DW to extract in clavengers apparatus @ 40oC. In another process I used only hexane for extraction in Clavengers apparatus. In both cases GCMS result was not impressive... Yes..I extract the leaves in clavengers apparatus using puew hexane...

But using hexane you do not obtain an essential oil. It is a simple solvent extraction. Furthermore, the distilled fraction is composed almost completely by hexane (the most volatile compound. To obtain the essential oil it is necessary that the two phases are immiscible. Only in this way the Dalton's law applies and you have a gas phase enriched in essential oil which can be extracted at a relatively low temperature (

So Dr. Guido is there any other alternates available for extracting the essential oil.....certain authors did with such volatile organic solvents....and they got good publishable results....

Hydrodistillation is the best method. If you do not obtain an appreciable amount of oil, sometimes it can be useful to put a small volume of hexane in the lateral arm where to trap the distilled volatiles.

However, it seems that your main problem is the differences of your GC-MS results with respect to those from previous studies. There are two possibilities: your plant material really produces a different essential oil or you have some problems with your instrument. Have you checked its proper working with a mixture obtained from pure standards? Have you properly tuned up the instrument? (i.e. cal gas, radiofrequency, etc?)

Dr. Guido,

Previously one lab colleague extracted turmeric oil from the same instrument and she got good result (over 60 compounds were found) and was much on lines with the article she followed...I am using Clavengers apparatus and is perfectly in tune I hope so and my extraction temperature is 40oC. I dont think the plant do really produce some different oils,,,,something is going wrong but cant point out.....does the dilution of oil with solvent do have any impact while doing GCMS?

GC-MS instruments should be tuned-up often, at least once a week. If some parameters such as mass calibration or radiofrequency are not optimized, you may obtain bad results.

Furthermore, I do not understand how you can perform hydrodistillation at 40°C. You need to boil to obtain vapor. Even if, according to Dalton's law, the boiling temperature of a mixture of not-miscible liquids is lesser than that of the more volatile component (water), it is at least 97-98°C due to its large excess with respect to the essential oil

Well Dr. Guido what I do is as is told that the heating is maintained at 40oC in the Clavengers apparatus....and the solvent (water) accumulates heat slowly start evaporating along with the oils....I intentionally kept the temp. at 40oC to avoid destruction of essential oil compounds?...Am I correct in what ever I am doing?...Can you please tell me your methodology in extracting of essential oils...so that I may try it out in my lab..

I have always set the temperature at about 100°C. I can observe a vigorous bubbling during the distillation

ok....and Dr. Guido can you please explain the steps that you follow from preparation of plant material to loading in to the clavengers and finally extracting oil...please...in practical way it will be more useful...

I coarsely cut the plant material and I put it inside a 2 liters round-bottom flask until it reaches about 2/3rd of the volume. Then I add water (about half flask) and I heat using an electric heater that maintains the temperature around 100°C. I fill the arm of the Clevenger with water and I distill for 2-3 hours. The oil accumulate on the surface of the water in the Clevenger arm. Here it can easily recovered and stored in refrigerator (5°C) until analysis. For the analysis I dissolve the e.o. in HPLC-grade hexane (10% solution). If the yield of the e.o. is too low, then I put a small volume of hexane (HPLC-grade) in the Clevenger arm and the volatiles dissolve in it. When ready I directly inject this solution for the analysis

Dr. Guido you wrote a point saying "fill the arm of the clavenger with water"...what does it mean exactly?...

I have a Clevenger apparatus like the following one:

www.finesi.info/wp-content/uploads/2014/10/clevenger-apparatus-500x500.png

I fill with water the right part of the apparatus, i.e. from the tap on the lower left of the picture till the slanting tube level (completely filled). E.O. accumulates on the top of the water inside the vertical tube (under the bubble condenser), while water returns in the flask via the slanting tube

Thanks Dr. Guido...but I am unable to open the image link...can you just upload it here....so that I can follow up your advice for extracting the E.oil

I do not know how to upload an image here

try this one:

http://www.sohamscientific.co.uk/clevenger.html

Thanks for these information , its interested question