YL9120 UV/Vis Detector
4-4. Troubleshooting
Most problems with HPLC detectors are, in fact, caused by other parts of the system. Noisy and drifting
baselines, poor reproducibility in quantitative analysis, and similar problems are more often the result of
dissolved air bubbles, contaminated eluents, dirty samples, or damaged columns rather than of actual
problems with detector hardware. In order to focus more effectively on troubleshooting detector problems,
we will first discuss on-board diagnostic tips and later present a troubleshooting table organized by
symptom, cause and how to fix.
Problem Cause How to fix
Bubbles passing through cell. Degas solvent and/or supply back pressure to
the sample cell, also check all high pressure
fittings for leaks(both liquid and gasses)
External triggering device is creating
electrical noise.
Check electrical lines for good connection
and/or interference from broad cast radiation.
Check for ground loops.
1. Unstable
Baseline
Extremely large supply voltage
transient on the AC line
Remove systems that consume high power
from the AC line.
Sample cell windows are contaminated.Flush cell with solvents(methanol, acetone,
water, nitric(6N) acid, water) and check for
leaks.
Sample input line has a leak. Check all lines from the output of the column to
the input of the sample cell for leaks.
Bubble trapped in the sample cell. Increase flow rate and/or back pressure on cell.
Recorder or integrator is grounded and
is causing a "ground loop" problem.
Check recorder with voltmeter to see if either o
the signal inputs is grounded to case or earth
ground.
2. Irregular Baseline
Photodiode window is dirty or not held
down properly to the cell holder.
Remove and clean photodiode window.
Noise
Sample cell is not screwed down to the
main unit.
Check sample cell mounts and cell holder
assembly.
Output span of the detector does not
match input range of integrator.
Press event mark to see if the "spike" is
approximately 20% of scale.
External triggering device is causing a
ground loop problem.
Use only triggering device with ground isolated
from earth ground.
Contamination of sample cell windows
has occurred.
Clean cell by flushing with solvents (methanol,
acetone, water, nitric(5N) acid). Inspect cell and
photodiode for fingerprints and smudges and
clean if necessary.
3. Baseline Drift
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