Determination of lead in biological and environmental samples by203Pb isotope dilution substoichiometric method

A procedure for the determination of lead in various biological and environmental samples by²⁰³Pb radioisotope dilution substoichiometric method is presented. The accuracy of the method by comparison with the literature values of reference materials appears to be good. The standard deviation of the method is less than 10%, and detection limit is about 0.1 g of lead.     

Determination of microamounts strontium by substoichiometric isotope dilution analysis

The isotope dilution with substoichiometric separation for the determination of strontium has been investigated. Strontium can be extracted with a substoichiometric amount of bis-1,2-dicarbollylcobaltate in nitrobenzene in the presence of 15-crown-5. It has been found, that Li⁺, Mg²⁺, Ca²⁺ and Fe³⁺ do not interfere in the strontium determination but the high extraction of K⁺, Na⁺ and NH₄ ⁺ ions results in marked influence.     

Determination of caesium microamounts by isotope dilution with substoichiometric separation

Selectivity of isotope dilution analysis with substoichiometric separation for caesium determination has been investigated. Caesium can be extracted with a substoichiometric amounts of bis 1,2-dicarbollylcobaltate in nitrobenzene in the presence of dibenzo-18-crown-6. The method is selective. Other metal ions (K⁺, Na⁺, Mg²⁺, Ca²⁺, Fe³⁺, Al³⁺) do not interfere.     

Determination of iron in silicate rocks by substoichiometric radioisotope dilution analysis

Iron is determined in rocks by an isotope dilution method involving dissolution with hydro fluoric acid, extraction of iron(III) chloride into isopropyl methyl ketone, stripping with dilute nitric acid, and substoichiometric separation of the Fe-EDTA complex on a cation-exchange column. The precision and accuracy are 1.5% relative or better, as indicated by analyses of some U.S. Geological Survey standard rocks.     

Determination of trace elements and radioactive materials by substoichiometric isotope dilution analysis

Substoichiometric isotope dilution analysis has been applied for the determination of trace elements in liquid samples, of carrier content in radioisotope solution and of concentration of organic reagent. Cu in mineral acids and in ZnSe single crystal was determined by the substoichiometric extraction with dithizone. The values of 1.8 and 0.018 ppm in nitric acid and distilled one and of 1.4 and 0.44 ppm in ZnSe were obtained. Cu and P carrier contents in⁶⁴Cu and³²P solutions were determined by the substoichiometric extractions with dithizone in CCl₄ and with molybdic acid into MIBK in the series of the solutions adding various amounts of Cu or P carrier. An analogous method has been applied for the determination of dithizone and diethyldithiocarbamate solutions. The method was also applied for the determination of⁶⁰Co radioactivity in environmental samples. The analytical result of water samples is described.     

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.     

The determination of zinc by substoichiometric isotope dilution

Recently, R??I?KA et al. proposed a determination of zinc in highly pure germanium dioxide by a substoichiometric extraction technique. In the present work, the effects on the substoichiometric extraction of equilibrium time, pH and interfering ions were investigated by radioactive tracer techniques and spectrophotometric measurements. The sensitivity of the procedure is limited by the blanks and the addition of oxalate ions can give rise to inaccurate results. The specific activity of ⁶⁵Zn was also determined by substoichiometric extraction.     

Determination of zinc in environmental water by displacement substoichiometric isotope dilution analysis /DSIDA/

Trace amounts of Zn /ng.ml^–1/ were determined using a displacement reaction of /Zn²⁺/ org from the dithizone organic phase into the aqueous phase, with a substoichiometric amount of /Hg²⁺/ aq. The results were compared with direct substoichiometric IDA. Absorption spectrophotometry was used as a reference analysis.     

Multielement isotope dilution analysis by means of radiometric titration

A theoretical concept is derived for multielement isotope dilution analysis in a liquid-liquid extraction system. The practical performance is based on radiometric titration. To that purpose a prototype of a titration/extraction vessel with flow injection has been constructed. For calculations of the initial concentrations of the elements of interest from the experimental data, a computer program has been developed.     

Determination of lead in fresh and canned pineapple by isotope dilution mass spectrometry and isotope systematics

Pineapple stored in welded and soldered can was analysed for lead to assess the extent to which it is contaminated during processing and storage. To avoid contamination during analysis the samples were prepared in clean laboratory using ultra-clean procedures. The lead concentration was determined by isotope dilution mass spectrometry and the sources of lead were identified by their isotopic signature and quantified by isotope systematics. The results showed that the lead concentration in pineapple stored in the soldered cans (ca. 150 ng g^?1) was about 2.5 times that found in the welded cans and 60–80% of this lead was traced to the soldered joint using isotope systematics. The edible portion of a fresh pineapple contained < 0.85 ng g^?1 lead, showing that even pineapple in welded cans may be contaminated 80 times more than the natural level.     

Determination of thallium by isotopic dilution method using substoichiometric displacement

A new analytical procedure for the determination of thallium in a wide concentration range has been developed. The method of direct isotopic dilution (IDA) using carrier-free²⁰²Tl and the formerly developed procedure of substoichiometric displacement have been used for the determination of thallium content in various types of analyzed samples e.g. minerals, sediments, ion-exchangers, hydrothermal waters, etc. in the concentration range from several percent to 10^?4%, or subsequently down to 0.01 μg/ml in waters. The results obtained are compared with those of emission spectrometry and activation analysis using (γ, n) reaction. A good agreement was found.     

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.     

Determination of cobalt by substoichiometric extraction with β-hydroxy-naphthaldoxime

A substoichiometric radiochemical solventextraction method is described for the determination of cobalt, employing β-hydroxy-naphthaldoxime and chloroform as reagent and extractant, respectively. The extraction behaviour of the complex of cobalt with the reagent in the pH-range 8–9.5 and the effects of various metal ions on the extraction are critically studied. The method is used to determine the cobalt content in some pharmaceutical drugs.     

Determination of cobalt by substoichiometric extraction with β-hydroxy-naphthaldoxime

A substoichiometric radiochemical solventextraction method is described for the determination of cobalt, employing β-hydroxy-naphthaldoxime and chloroform as reagent and extractant, respectively. The extraction behaviour of the complex of cobalt with the reagent in the pH-range 8–9.5 and the effects of various metal ions on the extraction are critically studied. The method is used to determine the cobalt content in some pharmaceutical drugs. Received: 10 January 1997 / Revised: 11 March 1997 / Accepted: 25 March 1997     

Determination of the extraction constant of gold diethyldithiocarbamate dichloride by substoichiometric extraction

Radioactive gold(III) with radioactive palladium(II) as reference ion in a chloride medium was substoichiometrically extracted with zinc diethyldithiocarbamate in chloroform. A formula for calculation of the extraction constant of the gold(III) complex was derived, for which only the values of distribution ratios of gold and palladium between the two phases had to be measured experimentally. The extraction constant was found to be log K = 68.9 ± 0.4.     

Determination of fluoride in water samples by substoichiometric extraction with trimethylchlorosilane

The determination of fluoride in aqueous solutions by substoichiometric extraction was performed using a carrier-free spike of¹⁸F (T=110 m). The principle, the procedure of the determination and the results of some tap water and urine analysis are given.     

Measurement of lead isotope ratios in wine by ICP-MS and its applications to the determination of lead concentration by isotope dilution

 Methods are described for the accurate and precise determination of lead concentrations and the isotopic composition of lead in wine samples using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This method needs little sample preparation. A comparison with lead isotope ratios measured by Thermal Ionization Mass Spectrometry (TIMS) in three wine samples reveals a good agreement between the two techniques. The lead concentration in three certified wine samples were measured by isotope dilution (ID) and the results are compared with those obtained by external calibration ICP-MS. Received: 10 June 1996/Revised: 23 September 1996/Accepted: 30 September 1996     

Determination of histamine in port wines and grape juices by ion-pair extraction and stable isotope dilution GC-MS

Summary An isotope dilution, GC-MS method for the quantitation of histamine in wines and grape juices was assayed. This method includes isolation of histamine and its, deuterated analogue [α,α,β,β-²H₄]histamine, used as the labelled internal standard, by ion-pair extraction with bis-2-ethylhexylphosphate, conversion to the volatile derivative: tris-pentafluorobenzyl-histamine, capillary GC separation and measurement of the abundance ratio of the (M-181)⁺ ions from labelled and unlabelled derivatives. The method was successfully applied to the determination of histamine in several samples of Port wine, red and white table wine and grape juice. Data are given on detectability, linearity, repeatability and recovery.