Agilent 1260 Infinity RID User Manual 85
Optimizing the Refractive Index Detector
5
Refractive Index Detector Optimization
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 (p/n 0100-1847), which is delivered with the accessory kit of the
detector).
12 Consider solvent changes with time
Baseline drift can be caused by the tendency of certain solvents to change
over time. For example the acetonitrile content of acetonitrile/water
mixtures will decrease, tetrahydrofuran will form peroxides, the amount of
water in hygroscopic organic solvents will increase and solvents such as
tetrahydrofuran held in the reference cell may begin to regas.
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