Agilent Technologies 1290 Infinity LC System System Manual And Quick Reference page 45

3
Optimization of the Agilent 1290 Infinity LC System
How to Configure the Optimum Delay Volume
injection is made when the valve switches back to mainpass and the sample is
flushed onto the column. The valve remains in this position during analysis so
that the autosampler is continually flushed and hence the gradient has to flow
through this delay volume to reach the column. This can be eliminated by
switching the injection valve from mainpass to bypass after the injection has
been made and the injected sample has been flushed onto the column. In
practice this can be done a few seconds after injection and is activated by
selecting the "Automatic Delay Volume Reduction" (ADVR) function in the
autosampler setup menu. The Flush-out Factor (typically 5 times injection
volume) ensures that enough time is allowed to flush the sample out of the
injector before switching to bypass. This effectively reduces the system delay
volume from 125 µl to 50 µl.
When using ADVR it should be noted that the gradient has already started at
the pump at the instant of injection. The question should be asked whether the
gradient has already reached the autosampler, in which case a small step in
the gradient will result. This happens when the delay volume is less than the
flush-out volume and is not necessarily a problem but may be a factor to be
considered in a method transfer. With a flush-out factor of 5 and an injection
volume of 10 µl, the autosampler will allow 50 µl to pass through before
switching to bypass which, with a delay volume of 50 µl, means the gradient
just reached the injection valve. Smaller injection volumes will have no effect
but for larger injection volumes this will introduce a small step in the gradient.
The flow rate in use will also have an impact on the decision to use ADVR or
not. At 0.2 ml/min the delay time saved is 21 seconds while at 1.0 ml/min it is
4 seconds.
The ADVR function is unlikely to be suitable for applications involving
compounds which are known to cause carry-over problems.
To minimize peak dispersion and delay volume in the Thermostatted Column
Compartment the low dispersion heat exchanger must be installed. The low
dispersion heat exchanger is part of the capillary kits recommended for low
dispersion applications. The common capillary kit also includes narrow
0.12 mm i.d. capillaries. The built-in 3 µl and 6 µl heat exchangers are for
backwards compatibility and should only be used in case a conventional
method needs to be run on the system even though in this case also the low
dispersion heat exchanger could be used.
To maintain resolution in the Agilent 1290 Infinity Diode-array Detector the
Max-Light cartridge cell has a low dispersion volume ( volume 1.0 µl) and no
further volume optimization is required. In situations where the alternative
Agilent Max-Light high sensitivity cell is used to get higher sensitivity the cell
Agilent 1290 Infinity LC System Manual and Quick Reference 45