I have isolated a pure compound from a plant source which could be either hydrocarbon or fatty acid ester as it is known from the IR and NMR analysis. How can I come to know about its volatile nature so that it can be analyzed by Gas Chromatography- Mass Spectrometry for finding its mass?
Just check its boiling point. My preference is below 300C. If your compound posses boiling point below or equal to or slight higher then 300C you can safely subject it on GC_MS.
Actually this range is consider safer because the maximum temperature of most commonly utilizing GC column (TRB-5 or equivalent) is around 350C. While the working temperature (Oven temperature) normally kept 20C below the Maximum temperature of the column to increase the life of column.
Check the list of components known as the volatil compounds after identification by analysis methods of your compound, because of the biosynthesis origins of these volatil constituents.
Of course, If you take GC-MS analysis you will know the mass values of your compound (volatile). Volatile compounds only can run GC AND gc-ms. Non volatile compounds may run LC-MS. But still there is no complete librrary for LC-MS. If your compounds will evaporate or liquid nature its volatile nature.
you can analysed it by using
1- GC & GC MS
2- Using authentic saples
3- Retention Index
In the same manner but you have to place solid instead of liquid, first liquid melts then after some time it will start boiling.
for e.g Stearic acid is solid in nature its melting point is 69.6C while its boiling point is 383C.
Dear Dr. Sayed
we did not need solid because all volatile components can be analyzed as liquid oil
If the isolated compound is pure, a methanolic solution (the solution should be poorly concentrated) could be directly injected in an ESI-MS. ESI ionization is very mild and give less fragmentation. The molecular mass of the compound, as [M]+ or [M+Na]+ in the majority of cases is ever recognizable.
The same is for compounds with exchangeable protons which, in the negative ionization mode, are revealed as [M - H]- .
Dear A. El-Ghorab,
Mr. G. Balaji was asking how to determine the Boiling Point of Solid (kindly read above Mr. Balaji post). off-course when you analyze that compound you must have to dissolve it in a suitable solvent. but before that you must know that either it will comes out or stack in the column. In my experience it can be determine by boiling point.
Dear Dr. Sayed Ali
this only explenation how the compondes analysed on gc it deoned on volatility and type of column and the temp. program .
for determination of boiling this another way.
you should have all pure compounds to determind the bp.
Mr.Syed thanks for your answers. My worry is same whether the compound will come out or stack in the column. Thats why I wanted to know whether my compound is eligible for GC-MS. Boiling point could be a good way to check. But again how can i find the boiling point if goes over 300 degree. Kindly tell me how do you find out the boiling point practically?
Dear Balaji
when bp is more than 300 degree so you should change your thinking because gc column temp. max. 300 degree but you can make derevatization as ester if it is possible it depend on the structure of your compund
Dear Balaji,
kindly find the attached file hope it will help you.
You can direct place solid for ESI-MS by using Direct Injection mode of MS (if available in model which you are use).
Since, you collect the fraction from plant origin with a proper working procedure; hence the information about nature of constituents present in fraction can predict by literature and you select column according to that.
for e.g. let suppose according to the procedure which you have followed makes fraction fatty acid enrich then you select TRB-FFAP column which has ability to analyze free fatty acids without derivatization or you can convert these fatty acid into methyl ester (FAMEs) by reacting them with methanol and can be separate on TRB-Wax.
My suggestion is that always use guard column when you have limited information about your sample to secure the column.
Just put solid instead of liquid first its melts and becomes liquid then boil or decompose.
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