Agilent InfinityLab LC Series RID User Manual
80
5
Optimizing the Detector
Refractive Index Detector Optimization
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.
13
Eliminate mobile phase/column combination problems
Certain mobile phases in combination with specific columns can generate
long term baseline noise. For example acetonitrile/water mobile phases with
certain aminopropyl bonded phase columns. To eliminate the combination of
mobile phase and column as a cause of long term noise replace the column
with Restriction capillary (G1362-87301) and re-evaluate the detector
performance.
Potential Causes for Baseline Problems
Noise (short term)
Typically the sources for short term noise are either electronic (check the
settings for the peak widths, check for ambient sources of electronic noise) or
they are related to the solvents, their composition and flow (in order to verify this,
turn off the pump, consider degassing your solvents, use only premixed
solvents).
Wander (long term noise)
Excessive wander is an indication for a general system or environmental
instability (system or laboratory might not be thermally stable, control instrument
and laboratory temperature). Verify that the solvent properties are constant over
time (flush out contamination, use only stabilized and premixed solvents). Clean
the parts in the flow path and allow the system to be flushed out and equilibrated.
Drift
Excessive drift is an indication for a general system or environmental instability
(system or laboratory might not be thermally stable, control instrument and
laboratory temperature). Verify that the solvent properties are constant over time
(flush out of contamination, use only stabilized solvents). Clean parts in the flow
path and allow the system to be flushed out and equilibrated.