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ghost peak right at gradient change

Posted: Tue Nov 08, 2016 9:23 pm
by hplcnewuser1
Hi, I am running gradient 10-30min 70-100% B then isocratic hold untill 35min.
A is 0.1% tfa water B 90%ACN 0.1%tfa. right about 33min mar i see a small peak followed by a dip then baseine recovers where it should be. IS this normal for gradient to isocrating transition?
Could it be that 3min delay between gradient change at the time ghost peak is detected is time it takes flow to go from pump to detector?
Has anyone had this issue.
thank you

Re: ghost peak right at gradient change

Posted: Wed Nov 09, 2016 12:50 am
by HPLC chemist
Yes. It takes time to reach equilibration. Depending on your flow rate, tubing, and column length it could be 3 minutes. Disregard it (this peak could be due to changes in refractive index or UV absorbance between the mobile phases).