Scintillation fluid how does it work

The solvent portion of an LSC cocktail comprises from 60 - 99 percent of the total solution. When a radioisotope dissolved in the cocktail undergoes an emission event, it is highly probable that the particle or ray will encounter only solvent molecules before its energy is spent. For this reason, the solvent must act as an efficient collector of energy, and it must conduct that energy to the phosphor molecules instead of dissipating the energy by some other mechanism.

The solvent must not quench the scintillation of the phosphor, and, finally, the solvent must dissolve the phosphor to produce a stable, countable solution. Aromatic organics have proven to be the best solvents for LSC. The prototypical LSC solvent is toluene The solvents used in National Diagnostics scintillation fluids are safer and less toxic than toluene.

This captured energy is generally lost through transfer to another solvent molecule, as toluene has little tendency to emit light or undergo other alternate decay modes. The energy from these molecules passes back and forth among the solvent ring systems, allowing efficient capture by dissolved phosphors. Phosphors are broadly divided into two classes: primary and secondary scintillators.

Included at 0. The molecules of scintillator appear to induce a dipole moment in their solvation shell, allowing direct transfer of energy between the scintillator and excited solvent molecules separated by up to 10 other solvent molecules. Primary scintillators must be capable of being excited to a light emitting state by excited solvent molecules, and they must be soluble in the solvent at a sufficient concentration to give efficient energy capture.

Secondary scintillators, or wavelength shifters, were originally included in scintillation cocktails to compensate for the narrow spectral response of early photomultiplier tubes.

Most primary scintillators emit light below nm, but the response of early photomultiplier tubes drops significantly in this range. A secondary scintillator captures the fluorescence energy of the excited primary scintillator, and re-emits it as a longer wave length signal. The process by which this energy exchange takes place is not clear.

Although the emission spectrum of the primary scintillator and the absorption spectrum of the secondary scintillator generally overlap, the kinetics of the exchange suggest direct contact rather than an emission-absorption event.

While modern phototubes are generally capable of counting the light pulses from the primary scintillator, secondary scintillators have been found to improve efficiency in many cases and are still included in most cocktails. It has been found that linked benzene rings, rather than larger aromatic systems, generally make superior scintillators. Read more about quenching and quench correction. Quenching occurs when the energy emitted by a radioisotope is not transferred completely into light and therefore is not detected by the PMT of the counting instrument.

The decrease in final signal, as a result of quenching, can occur at various steps of the energy transfer process:. Liquid scintillation counting usually requires homogeneous mixing between sample and scintillation cocktail to ensure ultimate contact between analytes and solutes. Good mixing is needed in vials as well as microtiter plates. Many plates and vials exist, and the choice of what type of vial or plate to use will depend on factors such as volume, chemical resistance, safety, and performance in combination with the cocktail of choice.

You can view our Vials for Liquid Scintillation Counting and Microplate products to choose a vial or plate adapted to your application. Glass provides unparalleled optical clarity good visibility and is chemically inert, making it suitable for use with aggressive reagents and solvents.

However, glass vials can break when falling on the ground, increasing the risk of contamination. Borosilicate Pyrex glass is preferred due to its lower content of potassium, as compared with soda-glass. Potassium is the largest contributor to background in glass vials. A maximum volume of 20 mL is fixed due to the dimensions of current photomultiplier tubes 2 inch diameter.

Plastic exhibits lower background levels than glass, but be aware of static electricity. For this reason, anti-static vials are available. Plastic is combustible and therefore easier for waste disposal. In addition, it is shatterproof. Plastic polyethylene is produced from fossil petrochemicals and therefore is preferred because these raw materials contain minimal measurable background.

Scintillation results in the emission of light. In order to gain the best sensitivity, it is recommended to count plate-based assays in white microplates. If the plates are read from the bottom, such as on a MicroBeta, the plate should have a clear bottom No liquid scintillation cocktail is required, as scintillant is already embedded in the walls of the microplate. In assays using scintillation-embedded plates, separation of "positive" and "negative" signal from the radiochemical is achieved by designing the assay in such a way that the radiochemical is associated with the walls or base of the microplate and therefore able to interact with the scintillant under given conditions.

For example, in a cell-based uptake assay, radiochemical can only generate signal when taken up by the adherent cells, which are adhered to the base of the plate. They can discriminate between alpha- and beta- radiations, and also allow luminescence measurements. In addition to standard protocols using vial counters, radiometric assays can also be performed using higher-throughput detectors:.