Chromatography Forum

Dear All
I try to analyse stearic acid without derivatisation. I use FFAP column and Varian 1177 injector with gooseneck split/splitless liner. Injection method is splitless. Oven programmes from 200-260 degree celcius. The problem is I cannot set up the linear standard curve. Is this liner appropriate? Injector temp is 250.
Thank you
CPH SCU

This is very non-volatile fatty acid.

At best, cold on column might be a way to measure for trace amounts.

To do purity analysis, it is recommended that you derivitize the acid as a TMS ester or as a methyl ester.

A number of plates will be necessary to separate isomer fatty acids from stearic as well as the unsaturated C18 acids.

You might investigate fatty analysis analysis on different chromatography vendor web sites.

best wishes,

Rod

Long time back, i have used a FFAP column for analysis of fatty acids in Saw palmetto extract. It worked perfectly fine and i was using stearic acid as an internal standard. I did not develop the method and so i don't really know why an internal std method was setup.. May be you should try using some other fatty acid as an internal standard? offcourse, thats assuming that all you need is the assay of stearic acid in your samples. Also, i used the split mode to do it (with an Agilent 6890). I am assuming that you are in desperate need to improve your quantitation limit as you seem to prefer splitless. If you have enough analyte in your sample, then i guess split method should be the way to go.

When you say you cannot set up the calibration curve, what exactly do you mean? bad correlation? what is the R value for your curve?

Good luck!
Suresh.