Delay/Hold-Up Columns - Agilent Technologies 1260 Infinity User Manual

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Optimizing Performance
Optimizing Viscometer Performance

Delay/Hold-Up Columns

The delay columns play an important role in the viscometer operation.
While the polymer sample is passing through the detector's capillaries, the
hold- up columns delay the polymer elution across one side of the
viscometer bridge leading to an imbalance in the pressure across the
viscometer.
Once the sample passes through the delay columns, it creates a
"breakthrough" peak. The hold- up columns are of sufficient volume that
the breakthrough peak elutes after the sample peak has eluted.
The delay volume is provided by 2x delay columns that are fitted
internally to the viscometer assembly.
A typical chromatogram showing the "breakthrough" peak is shown below.
Figure 23 Typical viscometer chromatogramm
An early eluting "breakthrough" peak (too close to the DP sample peak
response) may indicate a problem with the stability of the delay columns.
Typically, the baseline noise that is expected from a viscometer should be
0.25 – 0.5 mV. Greater values are often a result of poor pump
performance. The pattern of baseline noise observed on a viscometer can
indicate the source of the problem.
Agilent MDS User Manual 113