18
General Features of Radioisotopic Methodology
latter are often applied as solubilizing or bleaching agents to decrease the
quenching in the samples. Therefore, when using such a treatment or when
working with samples rich in pigments, it is necessary after treatment to avoid
peroxides by using enzyme catalase or ascorbic acid, and to neutralize the acid
or the alkaline samples. Samples treated in this way or samples containing biologically activc pigmcnts should be previuusly controiled for chemoluminescence by counting analogous nonradioactive samples. This especially concerns
the samples to be counted for 3H, because the energy spectrum of chemoluminescence fits well with that of tritium.
Chemoluminescence differs from radioactive scintillation by the dependence of its counting rates on temperature, the temperature coefficient 010
being close to 2. In dioxane-based scintillation cocktails, it is larger than in
toluene cocktails. The most frequent mistakes caused by unaccounted chemoluminescence are connected with counting samples bleached with peroxides
(H20 2 or benzoyl-peroxide) after alkaline (NCS or KOH) hydrolysis without
previous neutralization of the samples after treatment, e.g., before the addition of peroxide. Such samples often produce severe chemoluminescence.
Therefore they should be neutralized to pH 7 with HCI solution after hydrolysis. After subsequent treatment with peroxide, the samples should be controlled for chemoluminescence using nonlabeled analogous material. If the
chemoluminescence still remains, the samples should be kept before counting
for 2 days at 30°C with the scintillation cocktail added until it fades. Another
way to decrease chemoluminescence after peroxide treatment is to destroy
its traces with catalase or ascorbic acid, or by heating the samples to 40-45°C
for several hours before adding the scintillation cocktail. If these hydrolyzed
samples become dry during this procedure, 1-2 ml of methoxyethanol or
ethanol should be added to dissolve the sediment, after which the scintillation
cocktail (preferably toluene-based) can be added.
1.2.3 Application of Radioisotopic Methods in Hydrobiology
The use and aims of sensItlve radioisotopic methods in hydrobiology in
general are similar to those in other branches of biology (Verkhovskaya 1955;
Rotshild 1962; Sheppard 1962; Sorokin 1975b; Faires and Boshwell1981; Smith
and Horner 1981). In aquatic environments, it is well known that the basic features of their physical, chemical, and biological regimes, as well as their productivity, form due to the metabolic activity of biological communities, e.g., via
the functioning of aquatic ecosystems. Radioisotopes are using in hydrobiological research to label molecules or substances to trace their metabolic transformations by aquatic biota, quantify their rates, investigate their localization
within organisms or biotopes, and understand their mechanisms. Radioisotopes are in use in all basic fields of hydro biological research, such as
productivity of aquatic communities, their trophical relationships, nutrient
General Features of Radioisotopic Methodology
latter are often applied as solubilizing or bleaching agents to decrease the
quenching in the samples. Therefore, when using such a treatment or when
working with samples rich in pigments, it is necessary after treatment to avoid
peroxides by using enzyme catalase or ascorbic acid, and to neutralize the acid
or the alkaline samples. Samples treated in this way or samples containing biologically activc pigmcnts should be previuusly controiled for chemoluminescence by counting analogous nonradioactive samples. This especially concerns
the samples to be counted for 3H, because the energy spectrum of chemoluminescence fits well with that of tritium.
Chemoluminescence differs from radioactive scintillation by the dependence of its counting rates on temperature, the temperature coefficient 010
being close to 2. In dioxane-based scintillation cocktails, it is larger than in
toluene cocktails. The most frequent mistakes caused by unaccounted chemoluminescence are connected with counting samples bleached with peroxides
(H20 2 or benzoyl-peroxide) after alkaline (NCS or KOH) hydrolysis without
previous neutralization of the samples after treatment, e.g., before the addition of peroxide. Such samples often produce severe chemoluminescence.
Therefore they should be neutralized to pH 7 with HCI solution after hydrolysis. After subsequent treatment with peroxide, the samples should be controlled for chemoluminescence using nonlabeled analogous material. If the
chemoluminescence still remains, the samples should be kept before counting
for 2 days at 30°C with the scintillation cocktail added until it fades. Another
way to decrease chemoluminescence after peroxide treatment is to destroy
its traces with catalase or ascorbic acid, or by heating the samples to 40-45°C
for several hours before adding the scintillation cocktail. If these hydrolyzed
samples become dry during this procedure, 1-2 ml of methoxyethanol or
ethanol should be added to dissolve the sediment, after which the scintillation
cocktail (preferably toluene-based) can be added.
1.2.3 Application of Radioisotopic Methods in Hydrobiology
The use and aims of sensItlve radioisotopic methods in hydrobiology in
general are similar to those in other branches of biology (Verkhovskaya 1955;
Rotshild 1962; Sheppard 1962; Sorokin 1975b; Faires and Boshwell1981; Smith
and Horner 1981). In aquatic environments, it is well known that the basic features of their physical, chemical, and biological regimes, as well as their productivity, form due to the metabolic activity of biological communities, e.g., via
the functioning of aquatic ecosystems. Radioisotopes are using in hydrobiological research to label molecules or substances to trace their metabolic transformations by aquatic biota, quantify their rates, investigate their localization
within organisms or biotopes, and understand their mechanisms. Radioisotopes are in use in all basic fields of hydro biological research, such as
productivity of aquatic communities, their trophical relationships, nutrient