Agilent 1290 Infinity II Flexible Pump User Manual 45
How to Optimize the Performance of Your Module
4
How to Achieve Higher Resolution
• F = flow (ml/min),
• V
m
= column delay volume,
• Δ%B = change in fraction of solvent B during the gradient,
• S = constant (ca. 4- 5 for small molecules).
This shows that k and hence resolution can be increased by having a
shallower gradient (2 to 5 %/min change is a guideline), higher flow rate
and a smaller volume column. This equation also shows how to speed up
an existing gradient – if the flow is doubled but the gradient time is
halved, k
*
remains constant and the separation looks the same but
happens in half the time. Recently published research has shown how a
shorter STM column (at temperatures above 40 °C) can generate higher
peak capacity than a longer STM column by virtue of running it faster.
(Refer to Petersson et al., J.Sep.Sci, 31, 2346- 2357, 2008, Maximizing
peak capacity and separation speed in liquid chromatography).
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