UV baseline unstable or intensity drops during the run
Posted: Tue 17 Mar 2015 13:10The UV baseline is unstable or its intensity drops during the run, what should I do?
The baseline is unstable:
There are 2 possible causes for this problem:
A/ The product has crystallised inside the UV cell:
Clean the cell with a high-throughput compatible solvent.
If cleaning is ineffective, place the UV cell in a sonicator bath, in a high-eluent solvent or in the presence of H2SO4 or HNO3 diluted ten- or twenty-fold.
If the UV cell is still not clean, then it will need to be replaced.
B/ The pH of the purification is too high:
Rinse the instrument and change the purification conditions.
The baseline intensity decreases during the run:
One of the purification solvents is UV-active.
Replace the solvent, or change the method wavelength.
The baseline is unstable:
There are 2 possible causes for this problem:
A/ The product has crystallised inside the UV cell:
Clean the cell with a high-throughput compatible solvent.
If cleaning is ineffective, place the UV cell in a sonicator bath, in a high-eluent solvent or in the presence of H2SO4 or HNO3 diluted ten- or twenty-fold.
If the UV cell is still not clean, then it will need to be replaced.
B/ The pH of the purification is too high:
Rinse the instrument and change the purification conditions.
The baseline intensity decreases during the run:
One of the purification solvents is UV-active.
Replace the solvent, or change the method wavelength.