Why peak shape goes on intraction with methanol

[chandusabini]

Dear all,

Please clarify that, why most of the peaks distorted in methanol or on increase of methanol content in diluent. Not only in HPLC but also in GC.

This is not in all case, most of the cases.


Regards
Chandrasekhar

[Consumer Products Guy]

It's tough to reply to such a general question. If your HPLC injection is in organic solvent, injecting too much (either microliters or organic) can distort peaks if you are starting with a high-aqueous mobile phase.

[JA]

Chandrasekhar,

Perhaps you can clarify on what you have observed experimentally? I agree with CPGuy that what you have asked is rather ambiguous but I will take a shot at a few possibilities. Further info on these can be found by using the search utility on this forum;

- strong solvent effect (mismatch with mobile phase)
- analyte lability (reaction)
- analyte/impurity solubility (ppt after injection)

Depending on the specific shape of your distorted peaks and anything you have seen to improve the situation, e.g. use of alternative diluent, injection volume or sample concentration, people might be able to better answer your question.