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Study Notes: LSC Troubleshooting

Liquid scintillation counting is a relatively simple technique to carry out but it relies heavily on the correct set-up of the LS Counter for the isotopes to be counted, correct samples, the correct LS Cocktail, the correct operation of the LSC and correct maintenance and calibration procedures being performed.

It is also sensitive to contamination of the LSC environment with small amounts of high activity materials.

Some of the common problems associated with LS Counting that should be considered when troubleshooting include:

Component
Comments
Sample

Correct Sample
Correct Volume
Sample contaminated with other materials
Sample is aqueous and mixed

LS Cocktail Correct Cocktail
Correct Volume
Low quench
Low Photoluminescence
Low Chemiluminescence
LS Vials Correct Vial
Clean and unused
Low quench
Low Photoluminescence
Low Chemiluminescence
Equilibrated for chemiluminescence or photoluminescence
Labelled correctly before transfer of sample and LS Cocktail
Placed into sample racks in correct order
Sample Racks Placed into LSC conveyor assembly correctly Correctly loaded with vials
Placed in correct orientation with respect to the counting chamber
LSC/Control Panel Turned on
Red and Green Channels set up correctly for appropriate isotopes
Vial locations correctly set
Correct count time set
CPM or DPM output selected
Run button pushed
LSC apparatus LSC turned on
Cleaned inside and out as required
Check for high activity spills using a Geiger-Mueller counter
Lid closed prior to counting
Routine maintenance and calibration carried out as required
Repairs by Becksley carried out as required
Computer Interface Turned on
Set-up correctly
Printer Turned on
Adequate paper for run
Service/Calibration Logs Filled out correctly to allow troubleshooting activities as required
Results Interpreted correctly by trained staff.
Recorded correctly

The key to safe and effective use of the LSC is:

  • Training of staff in:
    • LSC Operation
    • LSC errors and malfunctions
    • Interpretation of LSC results
    • Importance of routine maintenance and calibration.
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