We set out to determine the oxygen concentration of the argon-oxygen m
ixture in the technegas generator where technegas-like behavior change
s to pertechnegas-like behavior which allows [Tc-99m]pertechnetate to
enter the solution. Methods: We prepared radioaerosols analogous to te
chnegas and pertechnegas, with oxygen concentrations between 0% and 5%
. They then were examined by thin-layer chromatography using saline as
a solvent to measure the amount of [Tc-99]pertechnetate moving with t
he solvent front as a function of oxygen concentration. Results: The a
mount of mobile pertechnetate markedly increased when the radioaerosol
s were created in an atmosphere containing between 0.1% and 0.2% oxyge
n. The transition from technegas-like to pertechnegas-like behavior oc
curs when the oxygen-argon gas mixture contains lower concentrations o
f oxygen than those used in the preparation of pertechnegas. Conclusio
n: Argon intended for the preparation of technegas should contain no m
ore than 0.1% oxygen.