Sequential extraction separation for determination of technetium-99 in radwastes by ICP-MS

An approach based on sequential extraction separation and the subsequent ICP-MS measurement was introduced to determine ⁹⁹Tc in radioactive wastes. The radwastes were firstly alkaline-fused and the ⁹⁹Tc was separated by a sequential solvent extraction prior to ICP-MS measurement. NaDDC was selected as a chelation reagent in the solvent extraction processes. The influence of HCl and matrix concentration on the recovery yield and the effectiveness of removing isobar and unwanted radionuclides, such as ¹³⁷Cs, ⁵⁴Mn, ⁶⁰Co and ^110mAg, were evaluated. The designed sequential extraction procedure was optimized by an extraction experiment. The proposed technique is proven to be a simple and practical alternative for ⁹⁹Tc determination in low-level radioactive wastes; chemical separation of ⁹⁹Tc can be simplified and preconcentration such as precipitation and/or ion exchange, before the solvent extraction, can be excluded.     

Spectrophotometric determination of palladium with glyoxime and chloroform extraction

Palladium(II) reacts with glyoxime in a 1:2 mole ratio to form a yellow water-insoluble chelate, which is soluble in chloroform; the solution has an absorption maximum at 397 mμ. Absorbance measurements at 397 mμ allow determination of the palladium glyoximate in solution. The maximum amount of palladium is extracted at pH 1.0. Platinum(II), iridium(III), gold(III), and phosphate cause some positive interference, and iron(II, III) causes negative interference; the interferences can be eliminated by masking with EDTA. The species extracted has been shown to be identical with that used to prepare the original palladium glyoximate chloroform solution. With EDTA and multiple extractions, the method is satisfactory for the determination of palladium in the presence of other platinum-group elements and many other cations.     

The determination of technetium-99 in seawater and marine algae

Technetium-99 is preconcentrated from acidified seawater containing a trace of bromine by adsorbing it as the pertechnetate ion on the anion exchanger Duolite A101D. After elution with 4 M nitric acid, it is purified from other radionuclides by scavenging with hydrous iron(III) oxide and extracting from 5 M sodium hydroxide medium into methyl ethyl ketone. The organic phase is then evaporated and technetium is electrodeposited from oxalic acid medium onto a bronze disc and counted with a low background β-counter. Overall recovery is > 90% and the precision is ±0.2 pCi l^-1 at a technetium level of 0.6–1.0 pCi l^-1. Concentrations of the radionuclide in the central Irish Sea were found to lie in the range 0.4–2 pCi l^-1. The same analytical scheme can be used for determining the element in nitric acid digests of marine algae.     

Reactions of alkoxy(chloromethyl)methylsilanes with sodium diethyl phosphate and with sodium dimethylphosphinate

Summary The reactions of alkoxy(chloromethyl)methylsilanes with sodium diethyl phosphate and with sodium dimethylphosphinate provide a method for the preparation of some silicon-phosphorus organic compounds containing an Si-C-O-P linkage and functional groups attached to the silicon atom.     

Determination of technetium-99 in environmental samples by solvent extraction at controlled valence

Distribution coefficients of technetium and ruthenium are determined under different conditions with CCl₄, cyclohexanone, and 5% tri-isooctylamine (TIOA)/xylene. A method for analyzing⁹⁹Tc in environmental samples has been developed by solvent extraction in which the valences of technetium and ruthenium are controlled with H₂O₂ and NaClO. Technetium and ruthenium which are oxidized to TcO ₄ ^– and RuO ₄ ^– by NaClO are separated by extraction with CCl₄ at pH 4. The RuO ₄ ^– is reduced to low valence and technetium is kept in the TcO ₄ ^– state with H₂O₂. Technetium, ruthenium, and other nuclides are subsequently separated by solvent extraction with cyclohexanone and 5% TIOA/xylene. The decontamination of the procedure is 1.35·10⁵ for¹⁰³Ru and 1.66·10⁵ for^110mAg. The chemical yield of technetium-99 is 55%.On leave from Institute of Atomic Energy, Beijing, China     

Simultaneous determination of arsenic and antimony species in environmental samples using bis(trifluoroethyl)dithiocarbamate chelation and supercritical fluid chromatography.

Simultaneous separation and quantitation of arsenic(III) and antimony(III) can be achieved by extraction with lithium bis(trifluoroethyl)dithiocarbamate followed by supercritical fluid chromatographic (SFC) analysis. Arsenic(V) and antimony(V) are extracted after reduction with potassium iodide and sodium thiosulfate. Detection limits of 7 pg As and 11 pg Sb are achieved using this extraction method and SFC. Application to natural water and biological sample analysis is discussed.     

The extraction of iron(III) by dioctylarsinic acid in chloroform

Dioctylarsinic acid, HDOAA, in chloroform solution has been investigated as a reagent for the extraction of iron(III) chloride. The extraction coefficient reaches two maxima, one of 1.5 at 8.5 M hydrochloric acid and another of 7 at pH 2.3. Experiments in the range 4–8 M for sulfuric, nitric and perchloric acids showed no extraction of iron(III) from these solutions for extraction times of 6 h. Evidence for the extraction of H₃FeCl₆ from 4–9 M hydrochloric acid solutions as [(H₂DOAA)⁺]₃FeCl₆^3- is presented. The species extracted from aqueous solutions of pH 1–2.3 is probably a hydroxy complex of the composition [Fe₂(DOAA)₂(HDOAA)X₄(H₂0)₂ ](X = OH and/or Cl).     

Thermal decomposition kinetics of diethyl dithiocarbamate complexes of copper(II) and nickel(II)

Thermogravimetric (TG), derivative thermogravimetric (DTG) and differential thermal analysis (DTA) curves of CuL₂ and NiL₂ (L^?=diethyl dithiocarbamate anion) in air are studied. The main decomposition temperature ranges are: For CuL₂, DTG 250–350°, DTA 300–320° and for NiL₂, DTG 290–390°, DTA 360–400°. Mass loss considerations at the main decomposition stages indicate conversion of the complex to sulphides. Mathematical analysis of TG data shows that first order kinetics are applicable in both cases. Kinetic parameters (energy and entropy of activation and preexponential factor) are reported.

     

The extraction of niobium (V) and Tantalum (V) by Octylarsinic acid in chloroform

Dioctylarsinic acid (HDOAA) in chloroform solution extracts Nb(V) and Ta(V) efficiently from solutions containing oxalate and oxalic acid at hydrochloric acid concentrations greater than 1M.The extraction coefficients are 92.5 at 7M hydrochloric acid and 251 at 6M hydrochloric acid for niobium and tantalum, respectively. These metals can be extracted even more efficiently from sulfuric acid solutions. The results of the reagent- and pH-dependence studies suggested that a trimeric, monobasic oxoacid of niobium, associated with ten HDOAA molecules, is extracted. Tantalum appears to be present in the organic phase as (H₂DOAA)⁺ [Ta(C₂O₄)₃ (HDOAA_n] (n=l or 2).     

Spectrophotometric determination of tellurium in concentrates and brasses by chloroform extraction of the tellurium (IV) hexabromide-diantipyrylmethane complex after separations by iron collection and xanthate extraction

A method for determining 0.0001–0.10% of tellurium in copper, nickel, molybdenum, lead and zinc concentrates is described. After sample decomposition, tellurium is separated from most of the matrix elements by co-precipitation with hydrous ferric oxide from an ammoniacal medium. After reprecipitation of tellurium and iron, the precipitate is dissolved in 12M hydrochloric acid, tellurium(VI) is reduced to the quadrivalent state by heating, and separated from iron, lead and other co-precipitated elements by chloroform extraction of its xanthate. The yellow ion-association complex formed between tellurium(IV) hexabromide and diantipyrylmethane is extracted into chloroform from a 2M sulphuric acid-0.6M potassium bromide medium. The molar absorptivity of the complex is 1.82 × 10³ l.mole⁻¹.mm⁻¹ at 336 nm, the wavelength of maximum absorption. Small amounts of iron, copper and molybdenum are co-extracted as xanthates under the proposed conditions but do not cause error in the result. Interference from antimony, which is co-extracted as the chloro-complex, is eliminated by washing the extract with water. The proposed method is also applicable to brasses.     

Solvent extraction of Sb(III) with malachite green into chloroform

A rapid and selective method for the solvent extraction of Sb(III) using malachite green (C. I. Basic green 4) has been described. Effect of different parameters affecting the extraction coefficient value of Sb(III) such as acidity, time of equilibration, KI concentration, solvents, anions, etc. has been studied. For various elements the separation factor has been evaluated. The stoichiometry of the extracted species has been determined by the method of substoichiometric extraction. The decontamination factor for some elements using substoichiometric quantities of the extracting agent has been evaluated. Radiotracers were employed for the extraction studies. The method elaborated has been employed for the quantitative determination of antimony in normal, benign and cancerous tissues of the human brain.     

Solvent extraction of Os(IV) with 2-mercaptobenzothiazole into chloroform

2-mercaptobenzothiazole has been used for the solvent extraction of Os(IV) in acidic medium. The extraction of Os(IV) was found to be better than 90% over the pH range of 3.0 to 5.0 with an equilibration time of 5.0 minutes. The stoichiometry of metal:reagent determined by substoichiometric extraction and slope ratio method was found to be 1∶4. Decontamination factor for various elements in the substoichiometric extraction of Os(IV) were also evaluated.     

Spectrophotometric determination of tungsten in ores and steel by chloroform extraction of the tungsten-thiocyanate-diantipyrylmethane complex

A method for determining up to about 6% of tungsten in ores and mill products is described. It is based on the extraction of the yellow tungsten(V)-thiocyanate-diantipyrylmethane ion-association complex into chloroform from a 2.4M sulphuric acid-7.8M hydrochloric acid medium containing ammonium hydrogen fluoride as masking agent for niobium. The molar absorptivity of the complex is 1510 1. mole(-1).mm(-1) at 404 nm, the wavelength of maximum absorption. Moderate amounts of molybdenum and selenium may be present in the sample solution without causing appreciable error in the result. Interference from large amounts is avoided by separating these elements from tungsten by chloroform extraction of their xanthate complexes. Large amounts of copper interfere during the extraction of tungsten because of the precipitation of cuprous thiocyanate. Common ions, including uranium, vanadium, cobalt, titanium, arsenic and tellurium, do not interfere. The proposed method is also applicable to steel.     

Reaction of (ethoxycarbonylfuryl)methanephosphonates with diethyl carbonate in presence of sodium foil

Reaction of (ethoxycarbonylfuryl)methanephosphonates with diethyl carbonate in presence of sodium foil is studied. It is shown that if the acidifying group is conjugated with the carbanion center of 2-furylmethanephosphonate, addition of the carbanion to the carbonyl group of diethyl carbonate takes place to give 2-furylacetic acid derivatives in high yield. Sodium salts of these CH-acids are synthesized, isolated, and characterized. Their alkylation with alkyl bromoacetates is carried out. If ethoxycarbonyl group is not conjugated with the carbanion center, conversion of starting phosphonate and yield of adduct sharply decreases. Alkyl (2- and 4-ethoxycarbonylfur-3-yl)methanephosphonates immediately after acylation with diethyl carbonate are reduced with sodium-diethyl carbonate system to form alkyl 1-(2- and 4-ethoxycarbonylfur-3-yl)-ethanephosphonates. Formation of intermediate reduction product, the phosphorylated furylacetic aldehyde is also fixed spectroscopically. Simultaneously with the reduction dealkylation of ester group of starting phosphonates and alkyl 1-(3-furyl)ethanephosphonates takes place leading to the carboxylic acid salts. Alkyl (2-methyl-5-ethoxycarbonylfur-3-yl)methanephosphonate does not take part in condensation. It gives only the products of dealkylation under the action of sodium ethylate forming from diethyl carbonate.     

The solvent extraction of Ir(III) with 2-mercaptobenzothiazole into chloroform

Ideal conditions for the extraction of Ir(III) with 2-mercaptobenzothiazole (2-HMBT) into chloroform have been established. The effects of various parameters such as pH, time of equilibration, time of heating, solvents, cation and anion interferences have been studied. The stoichiometry of metal to reagent has been evaluated.     

EXAFS and IR structural study of platinum-based anticancer drugs' degradation by diethyl dithiocarbamate

Platinum compounds constitute a discrete class of DNA-damaging anticancer drug agents, including cisplatin, carboplatin, and oxaliplatin. The toxicity of such drugs raises the problem of waste detoxification. Diethyl dithiocarbamate (DDTC) is recommended by the World Heath Organization (WHO) for the destruction of cisplatin, but the degradation product has not been structurally characterized. This paper deals with the extended X-ray absorption fine structure (EXAFS) and IR structural study of the reaction products of DDTC with cisplatin, carboplatin, and oxaliplatin. Cisplatin and carboplatin give the same reaction product: Pt(DDTC)2. In the case of oxaliplatin, we observed the formation of [(diaminocyclohexane)(DDTC)Pt(II)]. In all cases, the replacement of labile ligands by strong ligands should lead to inactive compounds. Our results suggest that the WHO inactivation protocol might be extended to carboplatin and oxaliplatin. Nevertheless, this should be validated by toxicity tests of the degradation products.     

Spectrophotometric determination of ziram (dithiocarbamate fungicide) by thiocyanate and rhodamine 6G method

A sensitive spectrophotometric method has been developed for the determination of ziram in water, vegetables and grains. The method is based on the dissociation of dithiocarbamate complex of zinc with thiocyanate and rhodamine 6G at pH 4 to form a pink coloured complex that is stabilized by gelatin. The method is simple and Beer's law is obeyed over the concentration range of 0.05-1 ppm of ziram. The method is free from interference of similar dithiocarbamate fungicides containing Mn(2+) and Fe(3+) ions.