Geochemistry of Bulgarian soils in villages affected and not affected by Balkan endemic nephropathy: a pilot study.

Balkan endemic nephropathy (BEN) is a chronic tubulointerstitial disease whose mosaic-like distribution throughout the Balkans has not changed significantly since its initial description. In this study, we explored the hypothesis that the occurrence of BEN is linked with the environmental geochemistry of villages. Soil samples were collected from BEN and non-BEN villages in the Vratza region of Bulgaria. Samples were digested in nitric acid and analyzed for 22 elements by hexapole, inductively coupled plasma, and mass spectrometry. Selected results are that: 1) absolute concentrations from both types of villages were not enriched above "background" concentrations; and 2) copper, molybdenum, lead, and cadmium concentrations were higher in BEN than in non-BEN soils, while selenium concentrations were lower. Although geochemical differences between BEN and non-BEN villages were found, not all differences were statistically significant, in part due to a limited number of samples.

Atomic absorption spectrometry (AAS) - a versatile and selective detector for trace element speciation.

AAS as a highly sensitive and specific single element technique is ideally suited as a detector for speciation analysis. The combinations of chromatographic separation with element specific detectors (flame AAS, electrothermal AAS (ETAAS), hydride generation AAS (HGAAS)) provide powerful approaches to the determination of all species. Sample stabilisation is the area that requires most attention as it still represents the main source of problems encountered in speciation work. The correct speciation depends on how the sample is handled prior to analysis. Unfortunately, no universal procedure has been found. Anything that changes redox conditions, pH or complexation equilibrium is clearly unacceptable.

Flame AAS determination of dopants and trace metal impurities in single crystals of potassium titanylphosphate.

A flame AAS method is used for the determination of dopants and impurities in potassium titanylphosphate (KTP) single crystals. Sample digestion using sulphuric acid and hydrofluoric acid is proposed as being the most appropriate procedure. The effect of major and minor components in the sample solution on the analytical signal is studied. The content of the dopants Cr, Mn and Ni (at a level of about 1 mg g(-1)) as well as the content of the impurities Fe, Na, Mg, W and Al (from 4 mug g(-1), depending on the trace metal) in the KTP single crystals is determined. The precision of the method is characterized by a relative standard deviation of 3-10%. The accuracy is checked by comparison with ICP-AES data for the trace element content in the KTP single crystals.

Flame AAS determination of thallium in soils.

The anion-exchange enrichment of TlCl(-)(4) coupled to flame AAS is applied to the determination of the total, pseudo-total (not bound in the silicate matrix) and mobile (plant available) content of thallium in soils. Ascorbic acid is used as a new efficient eluent of thallium. The limit of detection of the method is 0.04,mug/g, the relative standard deviation at the 1 mug/g level is about 3%. The method is rapid and simple.

Determination of ortho- and pyrophosphates in waters by extraction chromatography and flow-injection analysis.

Extraction-chromatographic separation of ortho- and pyrophosphate anions on an inert support modified with an organotin extractant was studied and used for their subsequent determination in a flow-injection system. The proposed FIA manifold includes an extraction-chromatographic mini-column, on which the phosphate anions are separated and preconcentrated, and a post-column spectrophotometric detector. For the determination of orthophosphate, the absorbance of the reduced 12-molybdophosphoric acid is monitored at 660 nm. The sum of ortho- and pyrophosphate can be determined after preliminary hydrolysis of pyrophosphate to orthophosphate in neutral solution at 50 degrees by use of inorganic pyrophosphatase. For a sample volume of 6 ml, the calibration graph is linear within a range of 5.0-100.0 ng/ml P. The limit of detection is 0.3 ng/ml P. The recovery of the ions to be determined is not less than 96%, the relative error is not worse than 4%. The proposed method was used for the analysis of river water samples.

Composition of phosphoric acid solutions obtained when orthophosphoric acid is used as solvent for iron-containing samples by heating: The influence of nitric acid, sulphuric acid and iron(III).

The dissolution of an iron-containing substance in orthophosphoric acid either alone or mixed with nitric acid or nitric acid-sulphuric acid mixture at 270-280 degrees has been examined, to determine the composition of the solutions which are used for analytical determinations. The possibility of condensation of H(3)PO(4) and formation of polyphosphoric acids during the dissolution has been proved. Solutions which may contain pyrophosphoric acid, tripolyphosphoric acid and tetrapolyphosphoric acid have been obtained. The exact composition of these solutions depends on the initial H(3)PO(4) concentration, the heating time, and, in some cases, the presence of nitric acid and sulphuric acid. It is assumed that the nitric and sulphuric acid affect the loss of water and therefore the thermal dehydration of the orthophosphoric acid during the dissolution. No qualitative changes in the phosphoric acid composition have been observed in the presence of Fe(III). Formation of Fe(III) polyphosphates is assumed.

Separation of tellurium(IV) by solvent extraction methods.

A critical review is given of the contemporary state and the perspectives for development of solvent extraction methods for the separation of tellurium(IV). The literature (150 references) is covered up to the end of 1973.