base line Hump

[SRIMAN]

frequently we developed one method with ion pair reagent sodium perchlorate,we are observing during HPLC run a hump coming in the base line, is there any impact of ion par reagent on base line, but on injecting the blank, the baseline is good only, no hump is observed in the base line

column : INertsil ODS

[Kostas Petritis]

What is your detector?

[SRIMAN]

Photodiode array detector

[Chris Pohl]

SRIMAN,

There are quite a number of possible explanations depending upon your operating conditions. Can you tell us more about the composition of your mobile phase and your sample?

[alealbor]

What is your analyte?
Can you try to use Atlantis C18 columns with 0.05 % of TFA for high polar analyte?

Alejandro

[SRIMAN]

the Analyte is Ramipril and the method RS, i have taken is from EP, on new column C18, the base line hump is not appearing, but after few injections the base line hump is comming before the ramipril main peak,
can any one suggest me what is the main precaution to be taken to avoid this hump in the test sample for analysis.
this base line hump is not appearing in the blank.

[Chris Pohl]

SRIMAN,

I don't have access to EP methods. Can you tell us more about the composition of your mobile phase and your sample?

[Kostas Petritis]

Does the base line hump is affected with different injection amounts? i.e. if you inject twice as much does the hump change as well?

Ion pairing reagents can sometimes lead to such humps, the reason that you do not see it right away is due to (maybe) that your column was not fully equilibrated. These are also refered sometimes as system peaks...

You can also try to inject another basic compound to see if you get the same "baseline hump"...