Hello,
The HPLC equipment should I use has remained stationary for some time due to electrical problems.
Now the equipment has been repaired, but I have some problems with the baseline:
1) non-cyclic (erratic) noise, probably due to the fluid path, since the baseline improves significantly when the pumps are stops;
2) when the baseline stabilizes after 30-40 min of equilibrating, it does so on a negative value, regardless of the mobile phase used

Could you help please? Thanks