CHAPTER 12
200 PerkinElmer Life and Analytical Sciences
TR-LSC can be optimized for the latest generation of safer cocktail formulations
and for higher energy beta emitters. This is easily accomplished through the
instrument software by modifying the Delay Before Burst parameter on the Count
Corrections tab in Assay Definition. The Delay Before Burst feature functions by
implementing a time delay before afterpulse discrimination is enabled. This is
necessary because:
Scintillation cocktails that contain solvents based on di-isopropyl naphthalene
(DIN) and 1-phenylxylylethane (PXE) have long scintillation decay constants,
i.e. produce light pulses of longer duration.
Higher energy beta emitters produce longer duration pulses.
These phenomena must be considered in order to minimize the misclassification
of beta and background events, since the longer duration pulses arising from
either of these conditions mimic background pulses and may be eliminated by TR-
LSC. By increasing the time delay before afterpulse discrimination begins,
counting efficiency losses are minimized and sensitivity is increased.
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