Friends, I want to study the marigold oleoresin extracted using hexane in LC-MS/MS for confirming lutein esters. Also I would like to run a parallel sample which is saponified (with the esters removed) which is intended to contain pure lutein. I have gone through different articles but most of them use APCI as source for ionization. But I have only ESI source for ionization at my lab. Is it possible to follow the same procedures as that of APCI?
Also please help me in understanding the differences in the result output.
Thanking you very much.
Hi Surendra.
The diference between ESI source and APCI source is: ESI source: ionization process occur in the mobile phase with addition acid or basic compounds (Ex: Formic acid, or ammonium hidroxid) ESI ionization is used for analysis of polar compound.In APCI source: the ionization process occur in a corona needle, the ionization is performed for a electrical discharge in needle. APCI is used to ionizantion non polar molecules.
The marigold oil resin has a non polar caracteristic, and APCI uses in most common analysis.
In attached a articule about mass spectrometry explaining: APCI and ESI.
Hope this is help you.
Thank you very much Dr. Marcos. The article is of great help.
Also can I post doubts while going through the article?
Marcos is right! You would capture very little in ESI but worth trying it out. Without standard compounds and limited Databases such as Mass Bank, ReSpect and KnApSack DBs one would end up identifying very little of them.
APCI would be better, but then GC-MS with or without MSFTA/BSTFA derivatizations would be perfect to capture the non-polar oleo resin constituents.
Even with TLC- separation followed by MALDI-ToF-MS you would capture and identify many of those constituents.
Thanks,
Biswa
Misraji, thank you very much, for your suggestion. but I doubt using GC-MS because of the oven temperatures. Further, as articles suggest, many of the phytocompounds are studied well under LC-MS only according (to the magnitude that the literature available). Also, you said, "would capture very little in ESI but worth trying it out" feels me paradoxical whether to try or not.
One laboratory has told that, they can give the spectrum and molecular masses but cant name the compounds since he claims he dont have any library attached to his MS. How far will it be useful for me, if performed can I interpret the spectrum over internet easily, if so where?
Can you also explain the procedure for TLC followed by MALDI-TOF?
LC-MS spectra are very specific to the operating conditions of the analysis such as eluent, voltages, etc. used for the analysis t therefore on-line libraries are few. You literally have to be able to interpret the spectra to decide what might be the analyte then run a standard to verify it. The reason to try ESI is that some samples defy conventional wisdom.
The variables in EI GC-MS are more used in the transfer and separation of the sample rather than the degree of ionization, type of ionization, etc. EI spectra as in GC-MS spectra are pretty well documented in a variety of libraries. NIST and Wiley among others.
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