HPLC peak of the solvent

[anjali]

I have dissolved my sample in ethyl acetate for HPLC run and the mobile phase is methanol and water with acetic acid. Is it possible to get a peak of ethyl acetate also on injecting the sample? Is dere a need to identify the solvent peak(Ethyl acetate) prior to injecting the sample?

Also tell me can there be a difference in solvent polarity of the component on changing the column dimensions?

[Uncle Everett]

The UV cutoff for ethyl acetate is 256 nm. If you are using UV detection and your observed wavelength is <256 nm, you will see a peak for ethyl acetate, typically near the start of the run in the "solvent front".

If you can use a longer wavelength above 256 nm, the peak observed from ethyl acetate will become undetectable.

[tom jupille]

Other issues:

Ethyl acetate is immiscible with water. The methanol in the mobile phase will mitigate the problem somewhat, but you may still have problems.

Ethyl acetate would be an extremely strong solvent in reversed-phase. Using a strong-solvent diluent often causes peak shape problems.

For both the above reasons, keep the injection volumes as small as possible (and even then, there are no guarantees!).