Chromatographic Troubleshooting
Baseline symptoms
CIt can also result from valve operations: If valves are being switched during a run, examine the valve time program to see if the change coincides with a valve operation.
CThis symptom also can occur if the septum suddenly begins to leak; Avoid the problem by changing septa regularly.
COffset•see troubleshooting procedure for the particular detector in use.
Wander and drift
Baseline wander or drift may occur when a flow or temperature setting is changed. If the system is not stabilized at the new conditions before starting a run, some baseline changes are to be expected. Cases following assume that sufficient stabilization time has elapsed since the last change in operating conditions.
Wander and drift are often accompanied by noise, discussed below.
1.Baseline moves steadily upscale or downscale (drift) during the run:
C This is most frequently seen during temperature programming: Operation with a single column (no column compensation) at moderate to low attenuation causes this. If dual columns are used, check that the signal mode is correct for column compensation.
CIt is also possible the compensation is insufficient (upscale movement) or too great (downscale movement).
This cause of drift is minimized by thorough column conditioning. Operating at lower oven temperature also helps but prolongs the analysis. Use of a chromatographically equivalent column with higher temperature limit is also possible.
203