CHAPTER 11
192 PerkinElmer Life and Analytical Sciences
Detector
This is a device that is sensitive to radiation and can produce a response signal
suitable for measurement or analysis. In a liquid scintillation counter, this device
measures the light emitted as a result of the interaction between a scintillation
cocktail and an alpha or beta-emitting nuclide.
Discriminator
This is an electronic circuit which distinguishes signal pulses according to their
pulse height or voltage. It is used to exclude extraneous radiation counts or
background radiation. It is also used as the basis for pulse height analysis.
DPM
Disintegrations Per Minute. DPM are an expression of radionuclide activity. DPM
are calculated as follows:
Dual Label
This refers to a sample that contains two different radionuclides.
Efficiency
Efficiency is the ratio of measured counts to the number of decay events which
occur during a measurement interval. It is usually expressed as a percentage.
External Standard
An external standard is a radioactive source that is placed adjacent to a sample to
produce scintillation in the sample for the purpose of monitoring the sample’s
quench level. The TriCarb instruments use a Barium-133 source for this purpose.
Figure of Merit
Figure of merit is a term applied to a numerical value used to characterize the
performance of a system.
Flags, protocol
Protocol flags are numbered, plastic devices that contain an encoded, reflective
metal that the instrument uses to identify the appropriate assay counting
parameters for a set of samples. Physically place an appropriately numbered flag
on the first vial cassette of a group to identify the protocol that associates the
desired assay parameters.
Efficiency
Minute Per Counts
DPM =
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