Technical data

Agilent 1290 Infinity LC System Manual and Quick Reference 59

Optimization of the Agilent 1290 Infinity LC System

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.