Drar Jobair Ahmed,

Thanks for your interest. Firstly, I would suggest you to communicate with the company of HPLC, i meant the provided, they knows the things very well. Secondly, you may check your column, sometimes it is happened due to column. You may clean your column. I also suggest you to check your solvent purity..

DRIFT:

This probably has nothing to do with the company that supplied the HPLC system (unless of course it was purchased broken).

• To be addressed, concerns about HPLC "drift" must be expressed in numeric terms (e.g. voltage or signal units like mAU vs TIME). A detector's "Zero" point is an arbitrary point just used for reference. The degree of drift is what is important, relative to the baseline noise. The "drift" you describe may be of no concern at all or could indicate a problem with the method or HPLC. Without context to understand, we can not troubleshoot.

I can not tell from your post if the issue may be that you have not zero'd the detector at the start of the run or if it is something else. Sounds like you are running an isocratic method so the lack of regular washing with a strong solvent may lead to the column quickly fouling up. Before use, the column must be washed with a solution that is STRONGER than the mobile phase used to elute off any remaining material, THEN re-equilbrated back in the mobile phase. *This is a basic chromatography fundamental.

When you start an analysis with a UV/VIS detector, first, the column must be fully equilbrated and stabilized (the detector too). This make take some time. Once the system is stable, you can zero the detector (to place the signal start at '0' on the 'Y' axis), then make the injection. When the analysis is complete, use a suitable method to wash the column, then re-equilibrate it again for the next sample (and repeat). If the system always strongly drifts in one direction (note, some drift is normal with all systems), then the equilibration may not be sufficient, the method of poor quality or an analysis parameter is changing (e.g. pump flow variation, temperature changes, degassing level, bad or failing lamp bulb, solvent composition change, leak, large back-pressure changes, the column may be damaged etc). Troubleshooting on-site would be required to find the true cause. In the meantime: Measure the drift. Measure the flow rate, Measure the temperature changes. Use a proper column wash method between runs, make sure the column is fully equilibrated and stable before starting another analysis.

Below is a link to a free article that may assist you.

• "HPLC Retention Time Drift, Change, Variability or Poor Reproducibility. Common Reasons for it"; https://hplctips.blogspot.com/2015/11/hplc-retention-time-drift-change.html

Got this from

https://www.sciencedirect.com/topics/computer-science/baseline-drift

"2.1 Baseline drift correction

Baseline drift is a very common problem in chromatographic studies. It is classified as a type of long-term noise and is defined as a change in the baseline position. This kind of drift is mainly caused by changes of temperature, or solvent programming and temperature effects on the detector [7]. In most cases, the drift is represented by a curve instead of a linear function. As a result, it induces errors in the determination of peak height and peak area, which are very important parameters for quantitative analysis. In practice, an artificial baseline is usually drawn beneath the peak (Fig. 1). The peak areas and heights determined will be either greater or smaller than the actual values, which depend on whether the true baseline has a convex or concave shape. Therefore, most analytical chemists prefer to find out the exact shape of the baseline and then to subtract it from the original raw chromatogram."

chapters have been dedicated to addressing this issue. It is normal and observed in my lab. The software will correct it in general situations.