Chromatography Forum

Hi
I have a problem,I want analysis the methanol,formic acid,ethanol in blood.
for preparation of satndard solution, I dont know that what solvent is good?
I use packed column(propak Q from supelco), GC shimudzu 14 A, FID.
I inject the serum directly, is it correct?
I use acetonitrile as a internal standard.
thanks

dear
I don’t have any idea about formic acid but u will get good response and separation of methanol and ethanol on porapack Q column because of low concentration it advisable to inject as such but I don’t have any idea about direct injection of serum if u had any experience for same u can go had. for Std preparation u can try water.



Raj B

dear
I don’t have any idea about formic acid but u will get good response and separation of methanol and ethanol on porapack Q column because of low concentration it advisable to inject as such but I don’t have any idea about direct injection of serum if u had any experience for same u can go had. for Std preparation u can try water.



Raj B

thank you
I use water and it is good.
I inject 50 ppm of methanol and ethanol, but the response of ethanol isnt good comparing with methanol (the response of ethanol is very very low).
please explain for me.

You will probably not have good success in any attempt of measuring free formic acetic or propanoic acids on a porous polymer column, especially in serum.

Your methanol peak appears to be high, this could be from decomposition of the serum or from an improperly made std or from another coeluting peak such as acetaldehyde or methyl amine.

You will have to replace the packed column often with serum. I would suggest a precolumn of the same packing for cost-effectiveness.

methanol by wt/vol has a FID response 74% that of ethanol. Ethanol should have a larger peak based on equal weights of alcohol in the same volumn of liquid. I would use isopropanol as an IStd. Acetonitrile elutes too closely to ethanol

Good luck in finding the source of your error.

Rod