Varian ProStar 340, Operation Manual

Page: 61 / 64

M
AINTENANCE AND
T
ROUBLESHOOTING
ProStar 340 UV/Vis Detector 35
Symptom Possible Cause Suggested Remedy
Output span of the
detector does not match
input range of recorder or
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.
Recorder baseline
drifts excessively. Contamination of sample
cell windows has
occurred. Flush cell with solvents (methanol,
acetone, water, 6N nitric acid,
water). Inspect cell and photodiode
for fingerprints and smudges and
clean if necessary.
Solvent from column is
changing absorption. Column is filled with UV absorbers
that are bleeding - replace column;
impure solvent is equilibrating with
the column. Replace solvent with
purer grade, switch to a longer
wavelength so that background
absorption fluctuates less.
Leakage in the lines from
column to flowcell. Check lines for leakage.
Tiny bubble trapped in the
sample cell. Increase flow rate and/or
backpressure.
Output span of detector
does not match input span
of recorder or integrator. Press Event Mark to check for a
20% full scale spike.
Large temperature
fluctuations are occurring. Remove detector from the source of
drafts of hot and cold air.
Flowcell, photodiode
assembly, or flowcell
cover is loose. Tighten thumbscrews fastening
flowcell holder and flowcell cover.