I. INTRODUCTION The importance of chelating sorbents in analytical chemistry has risen substantially in recent years. To a considerable extent this is explained by the fact that the methods of concentrating and separating chemical elements are widely used when they are determined in various objects. Sorption methods are distinguished by simplicity of implementation. They are convenient for concentrating from any, including large, volumes of solution, and are easily combined with different methods of elements determination. Owing to these advantages, the methods of concentration by sorption are successfully used in analytical chemistry.1 Concentration and separation with the help of chelating sorbents is characterized by a high selectivity and effectiveness which assures an increase in sensitivity and reliability of the subsequent determination of elements by different chemical, physicochemical, and physical methods.2

Chelating Sorbents in Analytical Chemistry

Review of chemical separation techniques applicable to alpha spectrometric measurements

Optimal methods for preparation, separation, and determination of radium isotopes in environmental and biological samples.

A novel 227Ac/223Ra extraction generator for nuclear medicine was developed. Its operation is based on selective extraction of 223Ra with a solution of chlorinated cobalt dicarbollide and polyethylene glycol in a polar diluent from a solution of a mineral acid and a complexing agent. Radium is stripped to any appropriate aqueous solution on adding TBP into the extractant. Trials performed in the manual mode showed that 223Ra is efficiently separated from the parent isotopes 227Ac and 227Th (decontamination factor of 223Ra from 227Ac and 227Th >106). It is the most convenient to use the 223Ra generator for the radionuclide production in a regional center, because it allows fairly simple production of large batches of 223Ra, avoiding problems associated with the need for skilled staff for working with the generator in a medical center and with the radiation-induced degradation of the matrix (ion-exchange resin).

Extraction generator of 223Ra for nuclear medicine

The analysis of 226Ra in natural waters can be tedious and time-consuming. For the determination and differentiation of activities of 226Ra and 222Rn in drinking water by γ-ray spectrometry a simple and fast method is presented. Activities of 226Ra > 0.5 Bq L−1 can be determined according to stabilization of the sample without further procedures. For a more sensitive detection sample volumes of up to 5 litres are applicable by a rapid precipitation procedure without large expenditure. Further laborious enrichment methods are not necessary. Thus, detection limits of 0.1 Bq L−1 can be obtained when using sample volumes of 5 litres. Therefore the method is suitable for the monitoring of radioactivity in drinking water samples in accordance with the legal guidance of the European Union.

Determination and differentiation of 226Ra and 222Rn by gamma-ray spectrometry in drinking water

A rapid radiochemical method has been developed for the separation of radium in the presence of excess calcium from environmental samples such as spring waters and marine sediments. Radium is preconcentrated by co-precipitation as carbonates along with other alkaline earths. Subsequently, most of the alkaline earths are complexed with EDTA at pH 7.5 and the solution is passed through a column of Zeokarb-225 (NH
 4
 +
 ). Radium, along with traces of calcium, is sorbed on the exchanger. Radium is desorbed with 2N HNO3 and finally coprecipitated with 400 μg of barium as isulfate. The alphas of226Ra are counted in a silicon surface barrier detector and228Ra betas are counted in an end-window GM Counter.

Rapid radiochemical separation of radium from environmental samples using ion-exchanger Zeokarb-225

A rapid method for the separation of radium in spring waters of Tuwa, Panchamahal district, Gujarat State, India, containing large amounts of calcium (0.5 g/l) has been developed. It consists of concentrating polyvalent cations from 21 samples using 10 g of carboxylate exchanger, Zeokarb 226 (NH
 4
 +
 ) and then precipitating radium as sulfate in the presence of 400 μg of barium.

A rapid method for the separation of radium from Tuwa spring waters for determining the activity ratio of223Ra/226Ra

Copper in distilled water is collected on Zeokarb 226(NH 4 + ) and irradiated with thermal neutrons. By comparison of the induced activity of 0.51 MeV photopeak of64Cu with that of a standard, irradiated under comparable conditions, copper at ppb levels is easily determined.

Use of a carboxylate exchanger in the determination of copper in distilled water by neutron activation analysis

When a mixture of rare earths, thorium, and uranium at pH 1.0 in sulfate medium is passed through a column (1.5 × 12 cm) of Dowex A-1(H+), rare earths pass through. Then thorium is eluted with 6 N hydrochloric acid and subsequently the uranium with 2 N nitric acid. When the mixture at pH 2.0 in nitrate medium and in the presence of 1,10-phenanthroline is fed to a column of ZeoKarb 226(H+), the rare earths pass through. Then thorium is eluted with 0.05 M EDTA at pH 4.5 and subsequently the uranium with 2 N hydrochloric acid. These separation schemes are successfully applied to the analysis of monazite samples.

P. K. Padmanabhan

Papers

Rapid radiochemical separation of radium from environmental samples using ion-exchanger Zeokarb-225

A rapid method for the separation of radium from Tuwa spring waters for determining the activity ratio of223Ra/226Ra

Use of a carboxylate exchanger in the determination of copper in distilled water by neutron activation analysis

Use of Dowex A-1(H+) and ZeoKarb 226(H+) for the Sequential Separation of Uranium, Thorium, and Rare Earths in Monazite

Behaviour of a carboxylic acid exchanger in the presence of 1,10-phenanthroline