Agilent InfinityLab LC Series RID User Manual
79
5
Optimizing the Detector
Refractive Index Detector Optimization
6
Control the optical unit temperature
Always control the optical unit temperature (heater =
ON)
for maximum
detector sensitivity or with samples that could precipitate in the sample cell at
room temperature and set an elevated optical unit temperature at least 5 °C
above ambient conditions.
7
Use an appropriate response time
For most applications a setting of 4 seconds is adequate. Only for high speed
analyses (short columns at high flow rates) a lower setting is recommended.
Bear in mind that even if the response time setting is too high fast peaks will
appear a little smaller and broader but retention time and peak areas are still
correct and reproducible.
8
Recycle mobile phase
Use the recycle valve to allow automatic recycling of mobile phase delivered
when no analysis is running. The pump flow can therefore continue
uninterrupted until the next analysis without wasting mobile phase solvents.
In addition the refractive index detector is always stabilized and ready for
immediate use.
9
Consider using a degasser
For many solvents you can achieve better baseline stability, when using a
degasser. For some solvents a degasser might not lead to a better baseline
quality.
10
Flush the degasser
If flow is stopped and mobile phase remains inside the on-line vacuum
degasser the solvent composition will change. When re-starting the flow or
when using new mobile phase flush each degasser channel used for 10
minutes at the maximum flow rate of the pump (with the purge valve of the
pump open to avoid a potential over-pressure in the RI detector’s flow cell).
11
Use pre-mixed solvents, only
Don’t use a pump for mixing solvents. When operating the RI detector
together with a quaternary pump, bypass the MCGV in the quaternary pump.
You have to virtually convert the quaternary pump into an isocratic one, by
directly connecting the solvent inlet tubing from degasser or solvent bottle to
the active inlet valve of the pump (use PEEK adapter 1/4-28 to 10-32
(0100-1847), which is delivered with the accessory kit of the detector).
