Determination of thorium isotopes in gas lantern mantles by alpha-spectrometry

A procedure for the determination of the three main isotopes of thorium in gas lantern mantles by alpha-spectrometry has been developed. The samples examined were dissolved in concentrated nitric acid and thorium was precipitated as hydroxide. Thorium was then dissolved in hydrochloric acid to be extracted into a TOPO solution, back-extracted with sulfuric acid, electrodeposited onto a steel disc and finally counted alpha-spectrometrically. The radiochemical recovery for thorium was 94% with a counting efficiency of 37%.     

Determination of thorium with organic reagents: different methods using p-aminosalicylic acid

p-Aminosalicylic acid (PAS) can be successfully utilized as a reagent for gravimetric and volumetric determination of thorium. A quantitative precipitate of thorium is obtained by adding a hot 2% solution of PAS, in the presence of a little ammonium acetate at a pH range between 4 and 5.6. The thorium salt filters, washes and ignites readily. Thorium content of the salt can be determined directly by ignition to thoria, and indirectly by the quantitative bromination of the organic ligand with bromide-bromate mixture or by iodination with iodine monochloride in glacial acetic acid solution at 0° C. The processes give comparable results.     

Determination of thorium with organic reagents: uses of some aryl fatty acids

Phenylacetic-, phenylpropionic- and 1-naphthylacetic acids show definite promise as precipitating agents for the gravimetric determination of thorium. They can separate thorium from cerite earth and monazite sand, from solutions having thoria: rare earth oxide ratio up to 1 : 40, 1 : 16 and 1 : 14 respectively, by a double precipitation method. Foreign ions such as calcium, barium, strontium, titanium, zinc etc. do not interfere in the determination, of thorium by these reagents. As the thorium salts of these three acids are basic in nature, each possessing an entirely different composition, the determination of thorium by direct weighing of the precipitates is not possible and in each case the ignition of the precipitate to thoria is essential.     

Solvent extraction of thorium from mixed organic — aqueous nitric acid media by try-n-octylphosphine oxide

The extraction equilibria of Th in tri-n-octylphosphine oxide (TOPO)–HNO₃–H₂O systems have been investigated in the absence and presence of water-miscible alcohols and acetone. The influence of TOPO concentration in an inert diluent (toluene) and the concentration of nitric acid and the water-miscible additives have been systematically examined. The slopes of the log-log plots of D_Th vs. the TOPO concentration (up to 0.02M) are found to be close to 3 over a wide range of polar phase compositions leading to a coordination number of 11 for Th. The D_Th values were determined as a function of the concentration of uranyl nitrate in the aqueous phase, while the effect of additives was also examined in the absence and presence of uranyl nitrate in the polar phase. The results show that at TOPO concentrations above about 2.5 · 10^–3 M (about 1%) in toluene, polymerization of the solvent occurs.     

Reverse micelle-mediated dispersive liquid-liquid microextraction of 2,4-dichlorophenoxyacetic acid and 4-chloro-2-methylphenoxyacetic acid

A supramolecular solvent consisting of reverse micelles of decanoic acid, dispersed in a continuous phase of tetrahydrofuran:water, was proposed as an efficient microextraction technique for extraction of selected chlorophenoxy acid herbicides from water samples prior to high-performance liquid chromatography UV determination. The disperser solvent (1.0 mL tetrahydrofuran) containing 20 mg decanoic acid was rapidly injected into 10.0 mL of water sample. After centrifugation, the reverse micelle-rich phase (25 ± 0.5 μL) was floated at top of the home-designed centrifuge tube. The solvent was collected and 20 μL of it was injected into high-performance liquid chromatography for analysis. The results showed that the in situ solvent formation and extraction process can be completed in a few seconds. Under the optimal conditions, limits of detection of the method for 4-chloro-2-methylphenoxyacetic acid and 2,4-dichlorophenoxyacetic acid were in the range of 0.5-0.8 μg L(-1) and the repeatability of the proposed method, expressed as relative standard deviation, varied in the range of 2.5-3.2%. Linearity was found to be in the range of 1-200 μg L(-1) and the preconcentration factors were between 148 and 157. The mean percentage recoveries exceeded 92.0% for all the spiking levels in real water samples.     

Determination of gas phase peroxyacetic acid using pre-column derivatization with organic sulfide reagents and liquid chromatography.

The first selective HPLC methods for the determination of peroxyacetic acid (PAA) in gas phase samples have been developed. PAA reacts with 2-([3-{2-[4-amino-2-(methylsulfanyl)phenyl]- 1-diazenyl}phenyl]sulfonyl)-1-ethanol (ADS) to form the corresponding sulfoxide. Sampling may be performed in impingers using aqueous solutions of the reagent or by test tubes with the reagent coated on a solid sorbent. Sulfide and sulfoxide are separated by means of HPLC and detected at a wavelength of 410 nm. The method is highly selective for PAA in the presence of hydrogen peroxide when sampling in impingers. A 10,000-fold excess of hydrogen peroxide leads to the same peak area compared to PAA. Limit of detection is 10(-8) mol PAA, thus corresponding to PAA concentration of 46 ppb when using a sampling time of 10 min with a flow-rate at 500 ml/min. Another sulfide reagent, methyl-p-tolyl sulfide (MTS) has been used in a similar way with impinger sampling. Major advantages of ADS towards MTS are improved UV-Vis spectroscopic properties and reduced volatility.     

Fast volatile organic compound recovery from soil standards for analysis by thermal desorption gas chromatography

The development of high-throughput environmental screening assays are needed to meet high-specification data quality objectives (DQOs) that require large numbers of samples to be taken and analysed rapidly. The acquisition and stabilisation of the sample is a key technical and operational challenge in analytical sequences associated with the determination of volatile organic compound (VOC) contamination of soils. Further the development of miniaturised and embedded analytical systems for environmental conditioning monitoring requires the development of new sampling techniques. A proof-of-concept study is described that shows how pressurised gas, in this case carbon dioxide, may be used to recover reversibly-bound VOCs from soil into an adsorbent sampler, and then analysed by thermal desorption-gas chromatography. The effects of the volume of the pressurised gas, the gas flow rate and the mass of the soil sample on the recovery efficiency and breakthrough from the adsorbent trap were investigated in a preliminary characterisation study. Two distinct approaches were identified. The first involved ventilation of the voids within the soil matrix to displace the soil-gas headspace, a rapid screening approach. The second involved a more prolonged purge of the matrix to strip reversibly bound species into the gas phase and hence pass them into the adsorbent trap, a purge and trap approach. The shortest possible sample processing time required to yield analytically useful responses was 5 s with the use of the headspace approach. In this case n-octane, benzene and toluene were recovered from conditioned spiked soil samples at concentrations in the range 42 to 1690 mg kg(-1). The limit of detection for the system was estimated to be no greater than 1.2 mg kg(-1). Using the purge and trap variant enabled recovery efficiencies greater than 93% to be achieved with liquid spikes of n-octane onto soil samples. These preliminary studies showed that a system based on this approach would need to balance recovery efficiency, time and analyte breakthrough from the adsorbent trap.     

Separation,purification and recovery of thorium from monazite leach liquors by counter-current extraction process

Journal of Radioanalytical and Nuclear Chemistry - Separation and purification of thorium from monazite leach liquors was investigated by counter current extraction process. The Primene JM-T...     

Effect of chlorinating reagents on Zr recovery from Zircaloy-4 hull wastes: reaction behavior simulation by using the HSC code

Chlorination reaction behavior of Zircaloy-4 (Zry-4) was simulated by using the HSC code for three different chlorinating reagents of Cl₂, HCl, and CCl₄. Four major components (Zr, Sn, Fe, and Cr) of Zry-4 and their oxides which were produced during an oxidative decladding process were considered for the theoretical calculation. The simulation results revealed that Cl₂ might convert metallic Zr, Sn, Fe, and Cr into their chloride forms, while oxides might not react with Cl₂ at 380 °C. When HCl was employed as the chlorinating reagent, it was suggested that metallic Zr, Sn, and Cr might react with HCl while Fe and oxides might not. In the case of CCl₄, it was shown that CCl₄ could react with all of the metallic and oxide components to produce most amount of ZrCl₄ when compared with Cl₂ and HCl cases. Reaction behavior of the chlorinating reagents with residual spent nuclear fuel constituents (U₃O₈, MoO₃, Pd, BaO, Y₂O₃, SrO, Rh₂O₃, RhO₂, La₂O₃, CeO₂, and Nd₂O₃) was also performed, and it was revealed that Cl₂ and HCl might produce (PdCl₂, BaCl₂, SrCl₂, RhCl₃, LaCl₃, and NdCl₃) and (BaCl₂, YCl₃, SrCl₂, RhCl₃, LaCl₃, and NdCl₃), respectively. Although these by-products are produced, it was suggested that highly pure ZrCl₄(g) which contains FeCl₃(g) and SnCl₄(g) as impurities might be recovered when Cl₂ or HCl is employed as a chlorinating reagent because other by-products have higher boiling point than the reaction temperature of this study (380 °C). On the other hand, the theoretical calculation results showed that CCl₄ might react with all the residual spent fuel constituents to produce additional gaseous impurities of UCl₆ and MoCl₅ to reduce the purity of ZrCl₄ product.     

Estimation of recovery by multistep purge-and-trap gas chromatographic-mass spectrometric analysis of honey volatiles

Calculation of volatile recovery in dynamic headspace techniques such as purge-and-trap (P&T) usually requires a calibration with standard compounds. When these are not available, application of mathematical models to the results obtained by multistep fractionation of a sample can be used for the estimation of recovery. A comparison of the fit quality of quantitative data (GC peak areas) using different calculation procedures and of the results of recovery estimation is presented for different honey volatiles. While models M1-M3 and M5 proposed in this paper correctly describe multistep experimental data for most honey compounds, other volatiles present a recovery behaviour which requires an additional parameter to be considered (models M4 and M6). For the last compounds, recovery is variable along the multistep procedure and the total amount cannot be accurately estimated by the use of multistep P&T fractionation.     

Removal, recovery, and recycling of triarylphosphonium-supported tin reagents for various organic transformations

Phosphonium-supported tin reagents and catalysts were prepared and were shown to be effective in Stille couplings, radical dehalogenations, radical cyclizations, and carbonyl allylations. Not only could the tin residues be removed from the crude reaction mixture through a phase separation process but also they could be recovered and recycled.     

Determination of hydrochloric acid in organic solutions by gas chromatography

Summary A method is described for the determination of small quantities of hydrochloric acid in two chlorinated organic solvents (CHCl₃ and CCl₄). An excess of gaseous ethylene oxide is added to a liquid sample; the 2-chloroethanol formed is then analyzed by gas chromatography. The procedure is simpler and more sensitive in comparison with other conventional methods. It can be modified for other organic solvents.D.G.R.C.S.T. grant.     

The extraction of thorium from nitric acid solutions by long-chain aliphatic amines

The partition of thorium between nitric acid solutions and solutions of long-chain aliphatic amines in benzene is described. The organic phase was examined by infrared spectroscopy. Tertiary amines are more efficient extractants for thorium than are secondary amines; the efficiency is enhanced when the alkyl chain is branched and is strongly influenced by the organic solvent used as diluent.     

在线GPC-GC/MS法测定苹果中2,4-D残留

建立在线GPC-GC/MS技术测定苹果中2,4-D残留的快速检测方法。采用正己烷振荡提取试样中2,4-D,正丁醇-H2SO4溶液衍生化,通过在线GPC-GC/MS系统自动完成从GPC净化、浓缩到GC/MS分析。该方法中2,4-D在实际样品检测中的平均加标回收率为87.9%~99.9%,相对标准偏差(RSD)为2.7%~8.1%。方法的检测限为0.005 mg/kg。     

Removal of 2,4-dichlorophenoxyacetic acid from aqueous solutions by partially characterized organophilic sepiolite: thermodynamic and kinetic calculations

The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on organophilic sepiolite (dodecylammonium sepiolite, DAS) was studied as a function of solution concentration and temperature. The observed adsorption rates were found to be equal to the first-order kinetics. The rate constants were calculated for temperatures ranging between 25 and 40 degrees C at constant concentration. The adsorption energies, E, and adsorption capacity, q(m), for 2,4-D adsorption on organophilic sepiolite was estimated using the Dubinin-Radushkevic equation. Thermodynamic parameters (Deltag(a), Deltah(a), Deltas(a)) were determined by a new approximation from the isotherm of 2,4-D adsorption on DAS. Also, DeltaS(0) and DeltaH(0) values were calculated from the van't Hoff equation. These isotherms were modeled according to the Freundlich and Dubinin-Radushkevic adsorption equations. The amount of adsorption of this herbicide on organophilic sepiolite was found to be dependent on the relative energies of adsorbent-adsorbate, adsorbate-solvent, and adsorbate-adsorbate interaction.     

Rapid determination of thorium in ores : Estimation of trace amounts of thorium in complex minerals and ores

A very rapid method for the estimation, of trace amounts of thorium up to 0.01 per cent. or thereabouts even in complex minerals like ilmenite and columbitetantalite has been described. Thorium is collected in an acid solution with phosphates of zirconium and titanium without prior separation of silica, after decomposition of the mineral with sodium peroxide. Thorium is next collected as fluoride with lanthanum as a carrier, precipitated as thorium iodate in potassium iodate-oxalic acid mixture and finally titrated against 0.01N sodium thiosulphate. Accurate results are obtained within a short time of two working days.     

Extraction of uranium, thorium and lanthanides using Cyanex-923: Their separations and recovery from monazite

The extraction behavior of uranium, thorium and lanthanides, represented by cerium and ytterbium, by Cyanex-923 has been investigated. The effect of different variables like the concentration of acids, metal ion and extractant, nature of diluent and temperature has been studied. A composition for the extracted U(VI) and Th(IV) species has been proposed. Based on the partition data some important binary and ternary separations involving the aforesaid metal ions have been achieved. The proposed procedure has been applied for the recovery of uranium, thorium and lanthanide fraction from monazite sand. The stability and regeneration capacity of the extractant have been evaluated.     

Preconcentration and recovery of uranium and thorium from Indian monazite sand by using a modified fly ash bed

Adsorption of uranium, as UO₂ ²⁺, and thorium, as Th⁴⁺, has been studied using a modified fly ash bed. Effects of pH and various ions like La³⁺, Fe³⁺, Ce⁴⁺, SiO₃ ^2- etc., have been examined. Synthetic mixtures of UO₂ ²⁺ and Th⁴⁺ in different concentrations were passed through the bed and eluted separately with various selective reagents viz. ammonium carbonate, sodium carbonate and acetic acid-sodium hydroxide buffer. Separations of these elements at ppm level are shown to be very effective. The separation of uranium and thorium in the presence of lanthanides in monazite sand has been studied successfully. In the analysis of monazite sand, the oxalate precipitation has been avoided. The method is simple and of very low cost. The modified fly ash bed can also be used to remove uranium from contaminated water.     

Structure and behavior of organic analytical reagents : Stability of chelates of 2-(o-hydroxyphenyl)-benzimidazole and analogous reagents1

Stabilities of chelates of 2-(o-hydroxyphenyl)-pyridine, 2-(o-hydroxyphenyl)-quinoline, 1-(o-hydroxyphenyl)-isoquinoline, 2-(o-hydroxyphenyl)-benzimidazole, and 2-(o-hydroxyphenyl)-imidazoline were determined by the Calvin-Bjerrum potentiometric titration technique. The results have been interpreted in terms of steric considerations.     

An investigation of the abnormal products from the reaction of 2-thenyl and benzyl grignard reagents by gas chromatography.

The products of the reaction of 2-thenylmagnesium chloride (I) with a variety of reagents has been studied by gas chromatography. Carbon dioxide and ethylene oxide produced significant amounts of 5-substituted (“para”) products as well as 3-substituted (“ortho”) and normal addition products. Several other reagents, including acetyl chloride and formaldehyde, produced mainly “ortho” products along with small amounts of normal products. The dependence of product distribution on temperature, added salts and solvent character was found to correlate with the reported rates of inversion about the carbon-magnesium bond in primary Grignard reagents. Blocking the “ortho” position, in 3-methyl-2-thenylmagnesium chloride, increased the proportion of “para” product from 3 to 33%. In addition, the reactions of benzylmagnesium chloride with certain reagents were re-examined.