Can samples be put on the HPLC after transesterification by Zinc acetate? Do I have to worry about contamination?

I'm trying to separate 2 peaks with retention times 0.1-0.2 minutes apart on the GC. The second peak is showing up as a shoulder and is the peak of interest. I believe the 2 peaks to be isomers of each other. I tried an isocratic hold for approximately 5 minutes and was not successful. Please help - I'm new at GC method development!!!!

First off, are you using GC (gas chromatography) or LC (liquid chromatography)? If it is GC, try re-posting on the GC message board. If you meant LC, then:
There are only two ways to improve resolution:
- move the peaks further apart
- make the peaks narrower.
In order to give more cogent advice, we would need more details (column type, dimensions and particle size, mobile phase composition and flow rate).

I'm trying to analyze for trimellitic anhydride using 1,2,4 trimethyl benzene tricarboxylate as external standards. The polymer samples have been transesterified using zinc acetate. The GC-FID has identified 1 peak as my standard, but analysis of samples show a shoulder peak as my desired peak. Based on known spiked samples, the shoulder appears to be my desired peak. The first peak is believed to be another carboxylate. I need help in setting up a method to separate these peaks.

HP6890 GC
Capillary column, HP19091J-413
HP-5 5% Phenyl Methyl Siloxane
Nominal Length: 30.0 m, Nominal diameter: 320.0 um
Gas type: Helium, Mode: split, constant flow, inital flow: 0.8 ml/min, inital pressure: 5.43 psi ave velocity: 17 cm/sec
FID detector: temp: 250 C
Hydrogen flow: 40.0 ml/min, air flow: 450 ml/min
constant makeup flow, makeup flow: 45.0 ml/min makeup gas: helium, lit offset: 2.0
Signal-Data range: 20 Hz

Need help on Oven ramp to separate out peaks.


The first question is a HPLC question that has come up by a manager---please forgive, first time posting!

You may need to try a column with different selectivity. My first guess would be to try a more polar phase such as a cyanopropyl or a wax-type, though neither may be suitable depending on the oven temperature you are currently using.