Sequential substoichiometric radiochemical separation of selenium,thallium and cadmium

A procedure for sequential radiochemical separation of Se(IV), Tl(I) and Cd(II) has been developed. This procedure involves substoichiometric solvent extraction of these ions with 2-mercaptobenzothiazole (2-HMBT) under different experimental conditions.     

Rapid automated batchwize radiochemical separation techniques

The basic principles and specific techniques of rapid, automated radiochemical separation techniques that use batchwize separation methods are reviewed.     

Some problems concerning the use of automated radiochemical separation systems in destructive neutron activation analysis

The present state of a long term program is reviewed. It was started to elaborate a remote controlled automated radiochemical processing system for the neutron activation analysis of biological materials. The system is based on wet ashing of the sample, followed by reactive desorption of some volatile components. The distillation residue is passed through a series of columns filled with selective ion screening materials to remove the matrix activity. The solution is thus “stripped” from the interfering radioions, and it is processed to single-elements through group separations using ion-exchange chromatographic techniques. Some special problems concerning this system are treated. (a) General aspects of the construction of a (semi)automated radiochemical processing system are discussed; (b) Comparison is made between various technical realizations of the same basic concept; (c) Some problems concerning the “reconstruction” of an already published processing system are outlined.     

A new method for the radiochemical separation of rubidium and cesium

The analytical reactions of bismuth iodide and stannic chloride with cesium and rubidium are used for the radiochemical separation of these two elements. The method consists in precipitating potassium, rubidium and cesium as their cobaltinitrites, selective isolation of cesium as cesium bismuth iodide from glacial acetic acid, and subsequent separation of rubidium from potassium as chlorostannate from conc. HCl. The results obtained by the present method for the rubidium and cesium contents of the different U.S.G.S. standard rock samples are compared with those reported using methods of comparable accuracy. The suitability of the method for the analysis of fall-out samples for their radiocesium (¹³⁷Cs) contents has been demonstrated.     

A new method for the radiochemical separation of copper from fission products

A new method for obtaining radiochemically pure⁶⁷Cu from highly active fission product solutions is described. The method is based on the solvent extraction of the Cu(II)-diethyldithiocarbamate complex in n-butyl acetate in the presence of hold-back carriers for Ni, Co, Mn, Mo, rare earths, Cd, Te and Sb, and subsequent purification steps involving scavengings for Ag, Ba, Sr and Fe followed by an anion-exchange purification step for decontamination from Te. Copper is finally extracted as the α-benzoin oxime complex in which form it is mounted and counted. The method has several advantages over other methods in that decontamination is very high and it is sufficiently fast considering the stringent radiochemical purity achieved. The⁶⁷Cu separated by this procedure from a one-day-old mixture of fission products arising from 10¹⁰ fissions was found to be completely free of any contamination.     

Advantages of a two-detector system in automated substoichiometric radioisotope dilution analysis

Automation widens the scope of substoichiometric radioisotope dilution analysis. This is because the very strict requirement of the manual method-chemical separation of exactly equal quantities of the test substance-need no longer be fulfilled: reproducibility of the determination is reached by means of automated operation and activity measurement. The theory given in this paper shows how the choice of suitable chemical reactions is widened and why the reliability and the advantages of isotope dilution analysis are secured by the use of a two-detector system.     

Determination of uranium by neutron activation analysis using substoichiometric separation

Three analytical methods for uranium by neutron activation are described. The methods are based on the substoichiometric separation of barium or lanthanum, which are the fission products of uranium-235 by neutron irradiation. Uranium contents in high purity materials were determined by the methods, which were found to be useful for the determination of a trace amounts of uranium.     

Coprecipitation as a means of separation in substoichiometric isotope dilution analysis

Coprecipitation is proposed as a means of obtaining the necessary separation in substoichiometric isotope dilution analysis. It is shown with examples that by applying coprecipitation for separation and by using complexometric and oxidimetric or reductometric reactions as the substoichiometric reaction, a wide field of complexometric determinations of metal ions (e.g., with EDTA) and many types of redox determinations open up for further investigations. The method is simple, not time-consuming and offers many possibilities owing to the freedom to select a suitable precipitate.     

Coprecipitation as a means of separation in substoichiometric isotope dilution analysis

Chromium has been determined by isotope dilution in artificial standards and in standard alloys using the substoichiometric principle. As a substoichiometric reaction the reduction of Cr(VI) to Cr(III) was used, followed by separation of these species by coprecipitation of the trivalent chromium on a Ti(OH)₄ precipitate. For amounts smaller than 1 μg the standard method had to be modified owing to spontaneous reduction of hexavalent chromium in the solution. Interferences from other metals, if they occur, can be easily overcome. The method is simple and inexpensive.     

Do we need radiochemical separation in activation analysis?

The optimization of neutron activation analysis with regard to detection limit and uncertainty of measurement using physical and chemical means is reviewed. Using selected examples it is demonstrated that radiochemical separation is the most effective means of optimization, especially in neutron activation analysis, because it yields the lowest detection limits and uncertainties. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of microamounts of barium by isotope dilution analysis with substoichiometric separation

In an open neutron reflection setup there are some basic design parameters that have an important influence on the value of the sensitivity. The effects of variations of such parameters in the sensitivity (S) were calculated applying the Monte Carlo N-particle transport code system MCNP-4A.     

Rapid radiochemical separation of selenium

A rapid separation of selenium based on the extraction of Se(IV) from 4M hydrobromic acid into benzene containing 1 % of phenol, is described. Recoveries of 99 % are achieved in less than 5 min. Oxidizing and reducing agents interfere. The separation is highly selective for selenium.     

Application of α-benzoinoxime for substoichiometric extractive separation of copper in activation analysis

A method has been developed for the substoichiometric extraction of copper with a solution of α-benzoinoxime in chloroform. The separation can be carried out in the absence or in the presence of tartaric acid at pH 6.8–7.0 and 9.5, respectively. In the presence of tartaric acid no interference has been observed. The method has been applied to the determination of copper in biological material, silicon, aluminium and kaolin by the neutron activation method.     

A fully automated catecholamines analyzer based on cartridge extraction and HPLC separation

Summary A fully automated analyzer is described for the HPLC analysis of catecholamines. Firstly urinary and plasma catecholamines are reacted with diphenylboronic acid giving a complex without requiring a pH-meter step. This complex is strongly retained on a C 18 cartridge and elution with acetic acid solutions shows recoveries higher than 90 %. The catecholamines are eluted also by the mobile phase employed for the HPLC’ analysis. An intelligent autosampler makes the complex and fills a loop with all the solvents necessary for the sample cleanup. It then inverts the flow and pumps the sample and the solvents throught the cartridge. In the elution step the disposable extraction cartridge is positioned on stream with the HPLC analytical column by an automatic sampler. The separation is performed by ion-pair reversed-phase high-performance liquid chromatography, with sodium dodecyl sulphate as pairing ion, a short analytical column and electrochemical detection. The HPLC analysis time is 3 min and the total sample turnover time is 8 min. The recoveries and the precision of the analyzer are given together with correlation with manual HPLC.     

Neutron activation determination of noble metals in rocks: A rapid radiochemical separation based on tellurium coprecipitation

A procedure is described for the determination of Pd, Au, Ir, and Pt in rocks at the ppb concentration level. After irradiation with thermal neutrons, powdered rock samples are fused with carriers and Na₂O₂−NaOH. The fusion cake is dissolved in dilute HCl, and the activated noble metals and carriers are coprecipitated as a group with Te, using Sn²⁺ as a reductant. Gamma and X-rays are counted on semi-conductor Ge deterctors. Yields are determined by reirradiation. Results are given for several rocks, including U.S.G.S. standards PCC-1 and W-1.     

Determination of cadmium in water samples by substoichiometric radiochemical method employing potassium ethyl xanthate

A radiochemical method has been developed for the determination of microgram amounts of cadmium based on the substoichiometric extraction of its 1:2 complex with potassium ethyl xanthate into 1:4 v/v mixture of pyridine and ethyl acetate from 2.5 M sodium formate. 10-90 micrograms of cadmium was determined with an average error of +/- 1.96%. The method developed was successfully applied to the determination of Cd contents in water samples.     

Application of Tri-n-octylamine for the substoichiometric separation of chromium(VI) in activation analysis

A method has been developed for the substoichiometric separation of Cr(VI) by extraction with tri-n-octylamine solution in benzene from 0.1M H₂SO₄ solution. The method has been applied to the determination of chromium in silicon and aluminium by the neutron activation method.