The Gamma-Ram radio-HPLC detector from LabLogic is suited to working on a daily basis with soft gamma emitters such as Iodine-125 and Tc-99, and with intermediate gammas with energies up to about 1MeV
Although beta counters are capable of such tasks on an occasional basis, their counting efficiencies are low and sometimes unacceptable, and their poor resolution precludes analysis of two gamma emitters in the same sample.
To overcome these shortcomings, the Gamma-Ram has a heavy lead shield and a well-type titanium-activated NaI crystal, which has greater stopping power for gammas, giving high counting efficiencies, even for more energetic isotopes, and superior resolution that makes dual isotope counting practical.
The detector employs a hermetically sealed crystal/photomultiplier assembly, and both variable and fixed volume counting cells are offered for use with HPLC eluates.
Suitable for low energy emitters only, the variable volume cell consists of a Teflon tubing coil wound around a mandrel.
The coil in turn is surrounded by a cylindrical tungsten sleeve that can be moved in or out with a micrometer, exposing more or less of the coil to the surrounding sodium iodide.
Effective volumes from about 15ul to 200ul are possible.
For unusually high activity levels or more energetic isotopes, fixed volume cells made of stainless steel chromatography tubing are recommended.
The U-shaped tubing is surrounded by a lead or tungsten plug except at the bottom, giving exposed volumes as small as 5ul.
This type of cell is especially useful for preparative work where the activity levels might otherwise overwhelm more conventional coil cells.
