How To Achieve Higher Resolution - Agilent Technologies 1290 Infinity User Manual

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How to Optimize the Performance of Your Module

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
• N=plate count (measure of column efficiency),
• α=selectivity (between two peaks),
• k
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 ways. N is
inversely proportional to the particle size and directly proportional to the
96
=resolution,
s
=retention factor of second peak (formerly called capacity factor).
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