Bio-Rad ChromLab™ Software - Manual (Page 257)

UV or UV/Vis Detector
Instrument Guide | 255
Baseline noise
continues when pumps
are turned off. External environmental influences
can cause noise spikes. If the spikes occur at regular
intervals (for example, every
20– 30 sec), check for the
presence of heating baths,
drying ovens, or other heating
devices on the same electrical
circuit or in close proximity to the
NGC system. Turn off these
devices to see if the problem
goes away.
The UV trace will not
zero.  Air bubbles are present in the
flow cell.
 The flow cell is dirty.
 Clean the interior of the flow
cell by passing 1 M sodium
hydroxide (NaOH), water,
methanol, and/or 0.5 M
HMnO
3
or other mineral acid
through the cell. Dry the
interior of the cell with a
stream of high purity nitrogen
gas (never use “house”
compressed air as it can
contain oil droplets).
Tip: Alternatively, inject 2
ml of Contrad (catalog
#176-4118) and let sit for 10
min. Flush cell with water
followed by 20% ethanol.
 Condensation can occur on
the exterior windows of the
flow cell when the optics unit
is moved from the lab to a
cold room and vice versa.
Always allow an equilibration
period to compensate for
such temperature effects.
Symptom Possible Cause Possible Solution