Agilent InfinityLab LC Series RID User Manual
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Optimizing the Detector
Refractive Index Detector Optimization
Detector Equilibration
The Refractive Index (RI) is a function of temperature, pressure and a property of
the used solvent (it changes with solvent composition, degassing level and due
to any trace of contamination). Therefore the Refractive Index Detector will
detect any change in any of these parameters as a change in its signal and a
variation of its baseline. Therefore the detector will trace down any instabilities in
the system and the environment as well. It may sometimes appear, as if the
detector itself was unstable or generating an unstable baseline, where in fact, the
detector is simply displaying the instabilities of the environment and the rest of
the system. By this the detector is often - without justification - blamed for
instabilities, which it does not generate itself, but only detect. The fact that this
detector is a universal detector makes it also sensitive to instabilities introduced
to it from outside the detector.
This makes it very important to have a very stable environment and system for
achieving best possible baseline stability. The baseline will get the better, the
longer the system is used under identical and stable conditions. Keep the
temperature in your laboratory and system constant and controlled. Ideally a
system with an RID should be used always with the same type of analysis (stable
solvent composition, temperature, flow rates, don’t switch the pump off after
analysis, instead just recycle solvents or at least reduce only the flow. Switch
valves and settings only when needed. Don’t expose the detector to draft of air or
to vibrations). A change of any of these parameters may require a considerable
amount of time for re-equilibration.
