Technical data

56 Agilent 1290 Infinity LC System Manual and Quick Reference

3 Optimization of the Agilent 1290 Infinity LC System

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 considers how resolution

can be increased by examining the following points:

• Optimize selectivity

• Smaller particle-size packing

• Longer Columns

• Shallower gradients, faster flow

• Minimal extra-column volume

• Optimize injection solvent and volume

• Fast enough data collection

Resolution between two peaks is described by the resolution equation:

where

• R

=resolution,

• N=plate count (measure of column efficiency),

• =selectivity (between two peaks),

• k

=retention factor of second peak (formerly called capacity factor).

The term that has the most significant effect on resolution is the selectivity, ,

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