| In the
case of
gradient separations, extra peaks that show up in standards, samples,
and blank gradients are usually caused by contamination of the weak
solvent. This can be confirmed by running a series of blank gradients
with increasing equilibration times between gradients. For example,
equilibrate the column for the usual time, then run a gradient (this is
simply to clean off the column); equilibrate again for the usual time,
then run a second gradient; equilibrate the column for three times the
usual time and run a third gradient. Compare the size of the extra
peaks in the second and third gradients. If the heights/areas of the
extra peaks increase with increasing equilibration time, this confirms
weak solvent contamination as the cause. |
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