changes in the area of blank peaks in the test chm.

[gilaneh]

Dear all
In the analysis of pregabalin according to the pharmacopoeia BP2023 Method A, a peak is observed in the blank, which is also present in the chromatogram of test solution, but the area of this peak changes and becomes larger and smaller and does not match with the area of the blank peak.
I would appreciate it if you have any experience share with me.
*blank exactly is the mobile phase.

I really appreciate your suggestions

Regards
Azam

[Multidimensional]

Two possibilities come to mind.
(1) Column Fouling. Your column is contaminated with sample from improper flushing after each analysis. "Old" sample now bleeds off. Solve by reducing the amount of material you load on the column and incorporate a high quality washing method AFTER the analysis method, which dissolved and flushes off any retained material. The column may require cleaning or replacement.
(2) You are observing "Carry Over" contamination. Time to have your HPLC undergo professional cleaning and maintenance servicing. "Carry-Over (Carryover) Contamination in HPLC and LC-MS Systems"; https://hplctips.blogspot.com/2015/02/c ... on-in.html