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4.5
Noisy Baseline
•
Mobile phase or post-column reagent contains light-absorbing impurities
Prepare all mobile phases and reagents with spectro-grade solvents, reagent-
grade chemicals, and ASTM Type I (or better) filtered, deionized water that
meets the specifications in
•
Leaking fittings
Locate the source of the leak and tighten (or replace) the liquid line
connection. For tightening requirements, refer to Installation of Dionex
Liquid Line Fittings (Document No. 031432). The manual is on the Thermo
Scientific Reference Library DVD (P/N 053891).
•
Insufficient time for system equilibration after turning on lamp(s) or
after changing mobile phase strength or composition
The lamps usually require 20 to 30 minutes to stabilize. For sensitive
applications work or for detector validation, allow at least 2 hours for the
lamps to stabilize. After installing a new lamp, allow from 8 to 24 hours for
the lamp to stabilize.
After changing mobile phases, allow 20 to 30 column volumes for the system
to stabilize.
•
Strongly-retained components from previous analysis are slowly eluting
To elute strongly-retained species, use a stronger mobile phase. Re-equilibrate
with the standard mobile phase before resuming routine operation.
Clean the column as instructed in the column manual. If the problem persists,
refer to the column manual for troubleshooting guidance.
•
Plot scale exaggerates baseline noise
If autoscale is selected, even a plot with low noise may fill the screen. Check
the Y-axis scale values.
•
Air bubbles in flow cell
Remove the trapped air (see
To prevent air from becoming trapped in the cell again, follow these steps:
•
Degas mobile phases and post-column reagents by vacuum degassing
or sparging with helium.
Doc. 065378-01 1/12
Table
B-1.
Section
5.3).
4 • Troubleshooting
75
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