Reduced Detector Sensitivity - ABB PGC2000 Operation And Service Manual

The peaks may in fact be too large and saturating the detector or column. The splitter may be out of
adjustment, or the liquid sample size may be too large. Possibly the detector gain jumper at the
detector electronics is not setup correctly. The sample valve may be injecting an excessively large
sample volume due to deformation or a scratch in sample stem or worn seals.
Sample will spill or leak out during this procedure. Consult MSDS sheets on file at
your location for safety requirements.
1. Perform Test Procedure 2 (Carrier and Makeup Gas Flow Adjustments).
2. Perform Test Procedure 30 (Checking Temperature Table Values), steps 1 and 2, to check or
modify attenuation value.
3. Check detector gain jumper and modify if necessary.
4. Repair sample valve (see "SAMPLE VALVE REPAIR" in Section 8). Check sample loop size.

Reduced Detector Sensitivity

Symptom: The chromatogram or peaks have reduced in size from that of a previous analysis. This is
also characterized as a reduction in detector sensitivity.
Cause: The attenuation could be set too high, making the chromatogram or peaks appear small.
Another possible cause is the wrong carrier gas is being used (e.g. helium used instead of nitrogen).
The peaks may be too small as a result of excessive sample splitting due to the splitter being out of
adjustment, or a small liquid sample volume injection. The sample groove in the sample valve stem
may be plugged or restricted. A programming error in sample valve on/off timing may not allow
adequate time for a proper sample injection. Sample valve actuation malfunction can cause
inadequate sample injection. Possibly the detector gain jumper configuration at the detector amplifier
is not set up correctly. The sample valve may have a defective or wrong stem installed. Low
polarizing voltage, defective Detector Amplifier, or "dirty" FID can also reduce sensitivity.
1. Perform Test Procedure 30 (Checking Temperature Table Values), steps 1 and 2, to check or
modify the attenuation setting.
2. Perform Test Procedure 2 (Carrier and Makeup Gas Flow Adjustments) to check carrier and
splitter flow rates.
3. Perform Test Procedure 33 (Checking Method Table Configuration) to check sample on/off time.
4. Perform Test Procedure 28 (FID Polarizing Voltage Test) to check polarizing voltage.
5. Perform Test Procedure 15 (FID Reduced Sensitivity).
6. Check detector gain jumper and modify if necessary.
7. Repair sample valve (see "SAMPLE VALVE REPAIR" in Section 8).
8. Inspect sample valve stem to check for scratches, deformation and plugging. Check loop size
and stem length.
2000-OSM, F1
WARNING
6-11