Radioactive Tracer
Chemical compound in
which one or more atoms have been replaced by a radioisotope.
Basic Assumptions for Tracer Use
Adsorption
Radiocolloids
Equilibrium reactions
Precipitation and crystallization
Electrochemical properties
Tracer separation methods
Radioactive isotopes are chemically
identical with stable isotopes of the same element
Radioactive nature of the isotope does not change the chemical and
physical properties. (decomposition, adsorption)
substitution of 14C for 12C in a compound of carbon does not change the type or strength of the chemical bonds nor does it affect the physical properties of the compound.
Attachment
of radionuclides to semicolloidal aggregates in solution.
Solution contains large molecules such as polymeric hydrolysis
products,tend to adsorb trace elements.
Dust, cellulose fibers, glass fragments, organic materials
Colloids
Mixture containing small particles, in the range of 10-1000nm
that do not dissolve in the solution.
Low concentration of radioactive tracers lead to the formation of solute species
that are not observed at equilibrium with macro amounts.
Trace metal concentrations used to study the properties of a metal ion at relatively high pH's without the interference of polymerization reactions
Help identify, observe or follow the
behavior of various physical, chemical or biological processes.
Electrolysis of solutions can be used for electrodeposition of a trace metal
on an electrode.
The concentrations of trace amounts of ions show the same redox behavior as
macro concentrations
Reduction and oxidation reactions can be carried out in solutions with trace
amounts of radioactive species.
Co-precipitation
The simultaneous precipitation of a normally soluble component with a macro-component from the same solution by the formation of mixed crystals, by adsorption, occlusion or mechanical entrapment.
Trace element is too dilute to precipitate by conventional means, it is typically coprecipitated with a carrier, a substance that has a similar crystalline structure that can incorporate the desired element.
separating an element.
eg: separation of francium from other radioactive elements by
coprecipitating it with cesium salts
Liquid-liquid (or solvent) extraction is a technique for selectively transferring a species between an aqueous solution and an organic phase by equilibrating the aqueous phase with an organic solvent.
Application
on a large scale for the production of valuable metals, such as U,
reprocessing spent nuclear fuels
determining equilibrium constants at trace metal concentrations for separation
identification of short lived radionuclides
Liquid partition chromatography(LPC)
is a liquid-liquid extraction where one of the liquid phases is stationary and attached to a supporting material, and the other liquid phase is mobile.
carried out with either the aqueous or the organic phase
stationary.
Solutes in contact with surfaces have a tendency to be adsorbed on the
surface.
Amount of radionuclide in the solution in low but in principle,
all the radioactive atoms could be adsorbed on the walls of the vessel
depends on the concentration, on the chemical state of the radionuclide
and on the nature of the container material