Chromatography Forum

am running gradient 5 to 95% organic (0.1% formic acid in ACN) using varion RP C18 column i am not be see the peak of sesquiterpene hydrocarbon epi aristolochene a sesquiterpen hydrocarbon..is this compound will not come out with this gradient? is it too greasy to come out? i am using shimadzu IT-TOF with shimadzu LC.
follwing is the link for chemical structure of compound which i can not paste here...
http://pubchem.ncbi.nlm.nih.gov/summary ... d=50135472

Hi.

Your molecule looks rather unpolar. I would go to 100% ACN. How do you want to see the peak? I don't think there is much UV absorption. And I also doubt it gets ionised.
TLC with dervatization seems a good solution. Or GC-FID.

Alex

This is LC-MS for Cenzyme Q10 on Unison UK-C8:
http://www.imtakt.com/TecInfo/TI207E.pdf

I don't know if you'll be able to get ionization on your molecule.
But you can try similar chromatographic (and APCI) conditions.

Hi! alex..i am using shimadzu IT-TOF detector..the concecntration of molecule may be in nanogram/ml quantity ..TLC way will be difficult..my best option i guess is to switch to normal phase ..i did try going 100% acn for more than 4 min my col is very small 2.1x50mm..so it should have come out i guess..anyway i am buying NP col..

Bryan i dont think Q10 method will work for my compound..

thanks a lot for your suggestions..

It looks like coenzyme q10 has the larger logP value:
http://pubchem.ncbi.nlm.nih.gov/summary ... loc=es_rss

So - I think there's a chance it will elute with UK-C8 with this method.

That being said - it also depends on your sample prep.
If you're extracting with a non-polar solvent - than perhaps
normal phase is the way to go.

It's an interesting analysis - please keep us posted!

Hi,

Can the molecule be detected? What does the UV spectrum look like? Is there any absorbtion that is different from the solvent?
As far as I know, the IT-TOF uses a ESI source. ESI sources are less sensitive on apolar substances. Do you get a decent MS on direct injection (in ACN)?
If you switch to NP, avoid solvents with significant UV absorption. Hexane/heptane and IPA could work.
Any literature information onseparation and detection?
Alex

We analyse sesquiterpenes using LC (RP, water/acetonitrile) - APCI - MS. Many have no appreciable UV absorbance, and certainly do not ionize at all with ESI. If you don't have APCI (or APPI), the other best option is GC-EI-MS.

all the best
Tony

Alex,

I did not see any literature information on that molecule ..i do not have standard to confirm uv absorbtion..i have to identify that in my fermentation broth..it could be present there in trace..without having standard it wil be hard to analyse that anyway..

we can not by APCI for now I have to stick with ESI source Tony..neither do we have GC EI-MS..

I have to analyse another molecule a diterpene hydrocarbon..ent kaurene..i do not see that comming out either with this method..and colum..I ran gradient of 0-100% ACN in 8 min,8-13 min 100% ACN..but do not see that peak either..all the literature has described normal phase method for this molecule...

for now we dont even have C8 column...i am waiting for my xterra C8 column then I iwll try CQ10 method suggested by bryan..

Back in the late '80s, I was using normal phase LC (Hexane/et-O-et) on a silica column to separate crustacean produced sesqueterpenes - using UV.
All terpenes have at least one double bond, so there should be a chromophore that works at or above 210nm...