Measurement of Radioactivity
7
in hydro biology, perhaps because of their vulnerability under field or ship
conditions.
Liquid scintillation techniques for counting radioactivity by use of organic
scintillation liquids appeared in the USA and Italy in 1949-1950. The endwindow G-M detectors remained in use by most hydrobiologists until the
mid-1970:s, when the :safe and comparatively transportable models of standard
liquid scintillation radiometers, spectrometers, appeared on the market. The
equipment for liquid scintillation counting of radioactivity of low energy emitters had been developed between the mid-1950s and mid-1960s, mainly for
biochemical research. Its use greatly promoted achievements in this field,
largely due to the use of the radioisotopes 3H, 14C, 32p, and 35S. Later, in
1970-1975, the liquid scintillation technique gradually replaced G-M counters
also in routine hydrological research; but the G-M end-window scalers still
remain of practical use in this branch of biological science. They are cheap,
portable, and many times safer in the field compared with liquid scintillation
counters. Also, they need no voluminous accessories, such as vials with scintillation liquid, which is important for field researchers. The most reasonable
mode of work is to have a portable G-M scalers in the field for preliminary
tentative control of results. The samples prepared on filters remain safe after
this procedure and their radioactivity can then be remeasured more precisely
with the aid of a liquid scintillation scalers in the laboratory. Moreover, for
hydrobiological research using cheap isotopes like 35S or with isotope emitters
which have high radiation energy C 2 P) the use of end-window counters with
a window of 15-20mm in diameter still may be useful in practice. It greatly
simplifies the procedure of counting radioactivity on filters with plankton or
with the sulfur or phosphorus compounds sedimented on them.
1.2.2 Liquid Scintillation Counting
1.2.2.1 Basic Principles
The method of liquid scintillation is based on the detection of radioactive radiation by means of fluor solution and a photomultiplier phototube. The scintillation fluor converts the energy of primary radioactive particles emitted by a
labeled substrate into the light pulses, which then are recorded by the phototube being converted into pulses of electrical charge. The latter are amplified,
discriminated, and counted by the scaling circuit. The basic feature of this
method is a high counting efficiency even of the low-energy emitters. The
radioactive sample is placed right into the scintillation solution. Being dissolved, suspended, or immersed into this solution, the material of the sample
is in close contact with the scintillation fluors. Therefore the distance between
the detector and the emitter is reduced to the molecular level. The problems
of the theory and practical use of liquid scintillation counting have been thor-
7
in hydro biology, perhaps because of their vulnerability under field or ship
conditions.
Liquid scintillation techniques for counting radioactivity by use of organic
scintillation liquids appeared in the USA and Italy in 1949-1950. The endwindow G-M detectors remained in use by most hydrobiologists until the
mid-1970:s, when the :safe and comparatively transportable models of standard
liquid scintillation radiometers, spectrometers, appeared on the market. The
equipment for liquid scintillation counting of radioactivity of low energy emitters had been developed between the mid-1950s and mid-1960s, mainly for
biochemical research. Its use greatly promoted achievements in this field,
largely due to the use of the radioisotopes 3H, 14C, 32p, and 35S. Later, in
1970-1975, the liquid scintillation technique gradually replaced G-M counters
also in routine hydrological research; but the G-M end-window scalers still
remain of practical use in this branch of biological science. They are cheap,
portable, and many times safer in the field compared with liquid scintillation
counters. Also, they need no voluminous accessories, such as vials with scintillation liquid, which is important for field researchers. The most reasonable
mode of work is to have a portable G-M scalers in the field for preliminary
tentative control of results. The samples prepared on filters remain safe after
this procedure and their radioactivity can then be remeasured more precisely
with the aid of a liquid scintillation scalers in the laboratory. Moreover, for
hydrobiological research using cheap isotopes like 35S or with isotope emitters
which have high radiation energy C 2 P) the use of end-window counters with
a window of 15-20mm in diameter still may be useful in practice. It greatly
simplifies the procedure of counting radioactivity on filters with plankton or
with the sulfur or phosphorus compounds sedimented on them.
1.2.2 Liquid Scintillation Counting
1.2.2.1 Basic Principles
The method of liquid scintillation is based on the detection of radioactive radiation by means of fluor solution and a photomultiplier phototube. The scintillation fluor converts the energy of primary radioactive particles emitted by a
labeled substrate into the light pulses, which then are recorded by the phototube being converted into pulses of electrical charge. The latter are amplified,
discriminated, and counted by the scaling circuit. The basic feature of this
method is a high counting efficiency even of the low-energy emitters. The
radioactive sample is placed right into the scintillation solution. Being dissolved, suspended, or immersed into this solution, the material of the sample
is in close contact with the scintillation fluors. Therefore the distance between
the detector and the emitter is reduced to the molecular level. The problems
of the theory and practical use of liquid scintillation counting have been thor-