How To Achieve Higher Sensitivity - Agilent Technologies 1290 Infinity LC System System Manual And Quick Reference

How to Achieve Higher Sensitivity

The sensitivity of a separation method is linked to the choice of stationary and
mobile phases as good separation with narrow peaks and a stable baseline
with minimal noise are desirable. The choice of instrument configuration will
have an effect and a major impact is the setup of the detector. This section
considers how sensitivity is affected by:
• Pump mixer volume
• Narrower columns
• Detector flow cell
• Detector parameters
In addition, the discussion on detector parameters also mentions the related
topics of selectivity and linearity.
Pump Mixer Volume
To achieve lowest baseline noise with UV detection, the standard delay volume
configuration with the 35 µl Jet Weaver is recommended for the 1290 Infinity
pump module. This is applicable for almost all applications but when using
TFA in the mobile phase, or other situations requiring more mixing, the larger
volume side of the Jet Weaver mixer should be used to minimize mixing noise.
Columns
Sensitivity is specified as a signal-to-noise ratio (S/N) and hence the need to
maximize peak height and minimize baseline noise. Any reduction in peak
dispersion will help to maintain peak height and so extra-column volume
should be minimized by use of short, narrow internal diameter, connection
capillaries and correctly installed fittings. Using smaller inner diameter
columns should result in higher peak height and is therefore ideal for
applications with limited sample amounts. If the same sample amount can be
injected on a smaller i.d. column, then the dilution due to column diameter
will be less and the sensitivity will increase. For example, decreasing the
column i.d. from 4.6 mm to 2.1 mm results in a theoretical gain in peak height
of 4.7 times due to the decreased dilution in the column. For a mass
spectrometer detector, the lower flow rates of narrow columns can result in
higher ionization efficiencies and therefore higher sensitivity.
Agilent 1290 Infinity LC System Manual and Quick Reference
Optimization of the Agilent 1290 Infinity LC System

How to Achieve Higher Sensitivity

3
59