Pulsed photoacoustic laser spectroscopy for the purpose of determining actinoids specific to various oxidation states in solutions

The pulsed laser-induced photoacoustic spectroscopy for the speciation of very low concentrations of actinoides in near neutral aquatic solutions is described. Special photoacoustic cells made of two identical piezoelectrical crystals coupled with quartz cuvettes containing the actinoide solutions provide the possibility of a differential measurement. With this technique, using gated detection with a boxcar-integrator, the solvent and window absorption effects are reduced. Following a simple theoretical description, the detection limit of this system can be estimated. Experiments with solutions of pure actinoide ions has shown that some of the oxidation states, such as Pu(IV), Pu(VI) and Am(III) can be detected down to 10-8 mol L-1. The linearity between the boxcar-signal and the actinoide concentration is demonstrated for an extended range over 4 orders of magnitude. Furthermore, qualitative measurements are made for hydrolysis reactions, carbonate complexation and polynucleation of Am-241, Pu-239 and Pu-238 in dilute solutions. With the help of ultrafiltration, photoacoustic spectroscopy is used for indirect detection of polynuclear species, colloids and microcolloids under various solution conditions. (orig.)