Determination of trace amount of Tc by laser induced photoacoustic spectroscopy.

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The radioactive nuclides, ^<99>Tc, has been of great interest from the view-point of global pollution. This nuclide is one of the most important fission products, because it is produced with comparatively high fission yield (6.06%). Because of its long half life (2.14 x 10^5 y) and a character of almost pure beta-emitter, its determination or detection can not be easily performed. In this study, the application of Laser Induced Photoacoustic Spectroscopy (LPAS) method to the determination of technetium was examined for the first time. A nitrogen gas laser was used to pump up a dye laser to obtain suitable monochromatic pulsed laser beam. A detection part which involves piezo-electric transducer (PZT) as a signal detector was home-made. Hexakis(thiourea)technetium(III) ([Tc(tu)6]^<3+>) and hexakis(isothiocyanato)technetium(IV) ([Tc(NCS)6]^<2->) complexes were chosen for the LPAS measurements. These complexes can be quantitatively obtained in the appropriate solution with simple chemical treatment, and they show intense absorption peaks near 500 nm region. Fast Fourier Transform (FFT) analysis was conducted after taking averaged signals. The FFT intensity was quantitatively observed for the wide range of technetium concentration for both complexes. The detection could be performed down to 10^<-8> M for [Tc(tu)6]^<3+> and to 10^<-9> M for [Tc(NCS)6]^<2->, respectively, showing 100 - 1000 times more sensitive than the ordinary colorimetric measurement.