K. Kratzer

Radiometric determination of stability constants of mercury species complexes with L-cysteine

Liquid-liquid distribution method has been applied for the determination of the composition and stability constants of mercury species with L-cysteine /H2L/. In the pH range 2–8, mercury /II/ forms a complex Hg/HL/2 with very high stability constant /lg β2 = 40.0/, whereas methylmercury and phenylmercury form complexes CH3HgHL /lg β1 = 15.56/ and C6H5HgHL /lg β1 = 16.5/. At pH≥13, anionic complexes HgL22− /lg β2 = 42.7/, CH3HgL− /lg β1 = 16.58/ and lg β1 = 17.7 are formed.

Determination of traces of bismuth by isotopic exchange reaction in the organic phase

A new radioanalytical method has been developed based on homogeneous isotopic exchange in the organic phase. The theory of the method is presented and discussed. This method has been applied for the simple, selective and rapid determination of bismuth based on the isotopic exchange between bismuth diethyldithiocarbamate and bismuth iodide complex labelled with210Bi. As little as 0.01 μg of the metal can be determined.

Radiochemical determination of intracellular ionic concentrations in alga Hydrodictyon reticulatum

Algal nets of Hydrodictyon reticulatum have been cultivated in the radioactivity labelled medium of different chemical composition. It has been found that the intracellular concentration of sodium, potassium, ammonium, chloride, sulphate and phosphate ions changed in a great extent in the dependence of the experimental conditions. The influx of cations from neutral chloride solutions decreases in the order: ammonium≫potassium, thallium/I/≥≥rubidium>cesium>lithium≫sodium ions. The intracellular chloride ions can be reversible displaced by bromide or sulphate anions.

Radiochemical study of the cumulation of phosphate on algal cells

The cumulation of phosphate on algae Scenedesmus obliquus and Chlorella kessleri has been investigated at different pH and concentration of phosphate in the absence and in the presence of various metal salts. Physico-chemical sorption on dead cells has been quantitatively described by the affinity constant KP (log KP=4.9±0.1). The cumulation on living cells is predominantly a metabolic process; the maximum relative rate of the cumulation was observed in neutral medium at lowest concentration of phosphate. The cumulation of phosphate was compared with that of arsenate (log KAs=4.8±0.1).

Selective extraction and separation of cadmium using tri-n-octylamine

The extraction of cadmium by tri-n-octylamine in benzene and cyclohexane from a mixture of sulphuric acid and potassium bromide has been investigated in detail. The optimum conditions for the extraction and back-extraction of cadmium have been found. The procedure for the concentration of cadmium is described and the separation of cadmium in the presence of more than 30 metals including fission products is presented.

Automated radioanalytical determination of lead and beryllium

The automated modification of the radioanalytical determination of lead and beryllium using AutoAnalyzer modules has been developed. The method for lead determination is based on a two-phase isotope exchange of lead between the sample solution labelled with212Pb and the standard lead diethyldithiocarbamate solution in carbon tetrachloride. For the determination of beryllium a substoichiometric isotope dilution method using7Be as tracer and acetylacetone in chloroform as extractant was used. As little as 0.02 μg/ml of lead and 2 μg/ml of beryllium can be determined by the methods above. The flow diagrams of the automated procedures are presented.

RADIOREAGENT METHOD FOR THE SELECTIVE DETERMINATION OF CYSTEINE

Liquid-liquid distribution method has been applied for the investigation of the complex formation of phenylmercury cation with different amino acids. It has been found that the stability constant of phenylmercury cysteinate is eight order higher in comparison with those of phenylmercury complexes with other amino acids which enables to develop a selective radioreagent method for the determination of submicrogram amounts of cysteine. The method is very simple because it consists in one minute shaking of labelled phenylmercury bromide in an organic solvent with an aqueous sample of cysteine and in the measuring of the radioactivity of the aqueous phase.

Changes of intracellular ionic concentrations and membrane transport in alga Hydrodictyon reticulatum

Algal nets of Hydrodictyon reticulatum have been cultivated in double or triple labelled medium as to investigate the change of the intracellular concentration and membrane transport of chloride, sulphate, phosphate and sodium ions. The change of the intracellular concentrations of potassium and ammonium ions has been studied using atomic absorption and spectrophotometric methods, respectively. The release of different ionic species from algal cells should be always taken into account during the membrane transport studies.

Radiochemical investigation of the bioaccumulation of urea by the alga Hydrodictyon reticulatum

It has been found that the bioaccumulation of14C-urea in the light is connected with the increase of pH-value of the external medium, with the increase of the intracellular concentration of ammonium ions and with the decrease of the intracellular concentration of potassium ions. The uptake rate does not depend on the concentration of urea in the range from 0.1 to 2.0 mmol dm−3 and it has a broad maximum at pH 6.5–8.0. The uptake rate of urea is a little higher compared with nitrite or nitrate anions, however it is at least three times lower in comparison with that of ammonium or hydrocarbonate ions. The uptake of urea in the dark leads to the increase of the intracellular concentration of ammonium ions, however, carbon dioxide formed is released from the cell.