Chromatography Forum

I'm using HPLC to determine the concentration of certain compounds on fish medicines. The medicines contain a mixture of the following compounds (in low concentrations) and between 80-95% dextrose:

Nifurpurinol
Acrinol
Malachite green oxalate
Metronidazole
Diflubenzuron
Cupric sulphate
Acriflavine
Citric Acid

Now, I've already used a polyamine II column (Acetonirtile/water 75/25) but some compounds coelute. A C18 column does not work at all. I'm now trying to optimize the gradient to see if I can resolve that problem. Does anybody have some experience with these compounds or suggestions????
Thanks a lot

You seems to have promising results by using HILIC conditions. While you still may need some other selectivity the ZIC®-HILIC column is an alternative.

Since you are using a gradient, I recommend that you initially run this from 5% to 50% buffer and then later tune the interval.

Usually you can try to separate complex mixtures of polar compounds with phenyl reversed phase columns, since it increases the retention of polar compounds and have a specific selectivity for molecules with pi orbitals.