Agilent 1290 Infinity II Flexible Pump User Manual 43
How to Optimize the Performance of Your Module
4
How to Achieve Higher Resolution
How to Achieve Higher Resolution
Increased resolution in a separation will improve the qualitative and
quantitative data analysis, allow more peaks to be separated or offer
further scope for speeding up the separation. This section explains how
resolution can be increased by examining the following points:
• Optimize selectivity
• Smaller particle- size packing
• Longer Columns
• Shallower gradients, faster flow
Resolution between two peaks is described by the resolution equation:
where
• R
s
=resolution,
• N=plate count (measure of column efficiency),
• α=selectivity (between two peaks),
• k
2
=retention factor of second peak (formerly called capacity factor).
The term that has the most significant effect on resolution is the
selectivity, α, and practically varying this term involves changing the type
of stationary phase (C18, C8, phenyl, nitrile etc.), the mobile phase and
temperature to maximize the selectivity differences between the solutes to
be separated. This is a substantial piece of work which is best done with
an automated method development system which allows a wide range of
conditions on different columns and mobile phases to be assessed in an
ordered scouting protocol. This section considers how to get higher
resolution with any chosen stationary and mobile phases. If an automated
method development system was used in the decision on phases it is likely
that short columns were used for fast analysis in each step of the
scouting.
The resolution equation shows that the next most significant term is the
plate count or efficiency, N, and this can be optimized in a number of
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