[en] The reliability of chemical processes can be greatly improved by implementing inline monitoring systems. Combining multivariate analysis with non-destructive sensors can enhance the process without interfering with the operation. Here, we present here hierarchical models using both principal component analysis and partial least square analysis developed for different chemical components representative of solvent extraction process streams. A training set of 380 samples and an external validation set of 95 samples were prepared and Near infrared and Raman spectral data as well as conductivity under variable temperature conditions were collected. The results from the models indicate that careful selection of the spectral range is important. By compressing the data through Principal Component Analysis (PCA), we lower the rank of the data set to its most dominant features while maintaining the key principal components to be used in the regression analysis. Within the studied data set, concentration of five chemical components were modeled; total nitrate (NO₃^-), total acid (H⁺), neodymium (Nd³⁺), sodium (Na⁺), and ionic strength (I.S.). The best overall model prediction for each of the species studied used a combined data set comprised of complementary techniques including NIR, Raman, and conductivity. Finally, our study shows that chemometric models are powerful but requires significant amount of carefully analyzed data to capture variations in the chemistry.

[en] The complexation of plutonium (III) with various aminopolyacetic acids is investigated by potentiometric titration at 25⁰C and at a constant ionic strength of 1 (KCl). The formation constants of the 1:1 complexes are reported for NTA, HEDTA, EDTA, DCTA and DTPA. The formation constants of the 1:2 complexes with NTA, HEDTA and EDTA as well as those of the mixed complexes formed between Pu(HEDTA) or Pu(EDTA) and NTA, IMDA or glycine are also reported. Several pK values of the 1:1, 1:2 and mixed complexes have been determined. These results are discussed within the framework of those obtained previously with the lanthanides. (Auth.)

[en] The very large chemical shift range provided by cobalt-59 yields well resolved lines for each of the nineteen isotopic species in the series of complexes ranging from Co(NH₃)₆³⁺ to Co(ND₃)₆³⁺ and each of the thirteen isotopic species in the similar series of tris(ethylene-diamine)cobalt(III) complexes. The relative intensity distribution of these n.m.r. signals at equilibrium is related directly to the proton isotope composition of the solvent. This n.m.r. method of quantifying the isotope composition is examined with respect to the equilibrium isotope effect and the application to determinations in aqueous and non-aqueous solvents. (Auth.)

[en] The use of a glassy carbon electrode for the anodic stripping voltammetry of silver, without deposition of a preliminary mercury film is described. The deposition time, scan rate, rotation speed and molarity of the sulfuric solution have been studied; the method is applied to the determination of silver in uranium and plutonium

[en] A rapid and sensitive procedure for the determination of antimony and arsenic in biological material is described. It is based on thermal neutron activation to ¹²²Sb (tsub(1/2)=2.7 d) and ⁷⁶As(tsub(1/2)=26.4 h), dry ashing with magnesium nitrate as the oxidizing agent and volatilization of the hydrides which are collected on an active carbon trap. This carbon adsorber is counted. The limit of determination is 5 ng g^-1 for both elements. (Auth.)

[en] A differential spectrophotometric determination of rhenium in its binary compound with uranium is described; the method is based on the action of tin(II) chloride on perrhenate in the presence of dimethylglyoxime with measurement at 445 nm. Uranium does not interfere. For solutions containing about 1 mg of rhenium, the coefficient of variation was 0.08%. (Auth.)

[en] A new gas chromatography/mass spectrometry procedure is described which simultaneously quantifies eight prostaglandins using one internal standard. The method could easily be extended to include more prostaglandins. The basis of the new method derives from two developments; 1) the discovery of quantitative chemospecific deuteration conditions for the C₅-C₆ double bonds of the prostaglandins (PG₂), and 2) the development of special computer software to solve the analytical problem. Eight prostaglandins, present in the 1-100 ppm range, were determined with errors only occasionally over 10%. Substantially better performance may be expected with a more stable mass spectrometer. Samples with only 2 prostaglandins showed errors only occasionally over 1%. (Auth.)

[en] The detection limit for tris(1,1,1-trifluoro-4-(2-thienyl)-2,4-butanediono)-europium(III) is established as 2 pg l^-1. A highly sensitive fluorimetric system consisting of a nitrogen laser and a pulse-gated photon counter is used. (Auth.)

[en] Investigations of signal enhancement in carbon-filament atomic absorption spectrometry are described. Several enhancements are shown to be due to preferential binding of the oxygen by the added interferent in the gas phase. This prevents the analyte atoms from reacting with the oxygen, thereby preserving or enhancing the atom concentration and thus the absorbance singal. (Auth.)

[en] A straightforward spectrophotometric method is described for the determination of uranium (VI) in trialkylamine sulphate extracts in kerosene diluent; 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) is used for colour formation without resort to back extraction into an aqueous phase. The method provides good tolerance to sulphate ion and rapid colour development and appears to be free from interference when applied to extracts from uranium sulphate leach liquors. (Auth.)