HPLC Products

Normal

Problem

To see a baseline shift like this requires a change in eluent. If using a gradient pump to mix the eluent, a change like this might occur after chnging the mobile phase ratios. If using an isocratic pump and premixing the eluent, this sort of baseline shift can occur when a new bottle of eluent is used. It shouldn't occur during a run. |When a change in the eluent is made, time should be allowed for the new eluent to work its way through the system, and even after the baseline shift is observed, time should be allowed for the system to re-equilibrate in the new mobile phase.

A more instant baseline shift is also observed when a wavelength change is made. So if a programmable UV detector is used, and wavelength changes are programmed into the run time, a baseline shift can be expected each time this occurs. This can be a problem for the integration programme, and it may be necessary to turn the Integration Off before the step, and on again after it. However since this is a timed event, care must then be taken to maintain accurate flow rates. Any change in conditions which affects peak retention times will then mean that the wavelength changes (and associated Integration Off steps) are in the wrong place.