Chromatography Forum

Hellow experts,

I have an polycyclic compound which is soluble in hexane and THF. I prepared a mobile phase THF : Water : : 80 :20 and prepare a solution in this condition and inject. I got peak at 5.2 minutes. When I repeated II nd injection the main peak is distorted. I did not understand what is the reason behind this. The pH of the compound is slight;y basic.

Best regards

Praveen

Are we talking about reversed-phase chromatography?
What's the retention factor of that peak? Absolute retention times doesn't say very much...
Column dimensions, flow-rate, injection volume, type of stationary phase?

If this IS reversed-phase than a mobile phase consisting of 80% THF is veeeeery strong - is your peak really retained?

Yes this is reverse phase chromatography, but my question is that how much % THF is safe for HPLC mobile phase is that any imect on pump seal when we use THF more than 50 %.

Before worrying about pump seals, my first question would be if you really need THAT much THF in your mobile phase. So again: Is your compound retained under these conditions?
If you really need more than 50% THF to elute your compound, I'd switch to a different stationary phase...oh, and just because your compound is soluble in THF doesn't mean that you must use THF in your mobile phase.

Yes my compound is much soluble in THF and if I use more than 50% THF in methanol I got very good peak shape.My worry is that more than 50% THF is safe for my pump seal or not, Just this.

Praveen

I'll try it again: What's the RETENTION FACTOR of your analyte?
My point is, you might be worrying about the wrong thing - good peak shape and long lasting pump seals doesn't help if your analyte is eluting in the solvent front!

Sidestepping the chromatography issue for a moment, the answer regarding pump seals is "it depends". Not all pump seals are made of the same material. You need to check with the instrument manufacturer/vendor to find out what they recommend.