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16 Agilent 1260 Infinity RID User Manual

1 Introduction to the Refractive Index Detector

Flow Path

The column eluent enters the optical unit through the in port and passes

through a heat exchanger. The combination of the heat exchanger and control

of the optical unit temperature in the range of 5 °C above ambient to 55 °CC

minimizes changes in refractive index due to temperature variations. The

eluent flows through the sample cell and via the same heat exchanger to the

purge valve. With the purge valve in the OFF position the eluent passes to the

recycle valve. If the recycle valve is also in the OFF/WASTE position the eluent

will flow via the waste port into the waste container.

If the recycle valve is in the ON/BOTTLE position the eluent will flow via the

recycle port back to the solvent bottle. The recycle valve can be manually set to

the ON or OFF position or the Automatic recycling after analysis mode can be

enabled. In this mode the recycle valve will automatically switch to the ON

position after each analysis has been completed and return to the OFF

position before the next analysis starts. Using this mode provides the benefits

of uninterrupted flow through the detector without the problems of excessive

solvent usage or the contamination of mobile phase with recycled sample

compounds.

If the purge valve is in the on position the eluent cannot pass immediately to

the recycle valve but will instead flow via a second heat exchanger through the

reference cell and then into the recycle valve (see Figure 5 on page 17).

Periodically switching the purge valve to the on position while only mobile

phase is flowing will ensure that the liquid in the reference cell is as similar as

possible to the flowing solvent. The purge valve can be manually set to the on

position for a defined time or the Automatic purge mode can be enabled. In this

mode the purge valve will automatically switch to the ON position for a

defined purgetime prior to the start of each analysis. If a purgetime is set then a

waittime must also be set to allow the detector baseline to stabilize after the

switching of the purge valve position.

After both the purgetime and waittime have been completed the analysis will

start. If the Automatic zero before analysis mode is enabled the detector output

will be set to zero immediately before the analysis begins.

Agilent Technologies Infinity 1260 User Manual

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