Anion analysis in uranium ore concentrates by ion chromatography

In the present exploratory study, the applicability of anionic impurities for attributing nuclear material to a certain chemical process or origin has been investigated. Anions (e.g., nitrate, sulphate, fluoride, chloride) originate from acids or salt solutions that are used for processing of solutions containing uranium or plutonium. The study focuses on uranium ore concentrates (“yellow cakes”) originating from different mines. Uranium is mined from different types of ore body and depending on the type of rock, different chemical processes for leaching, dissolving and precipitating the uranium need to be applied. Consequently, the anionic patterns observed in the products of these processes (the “ore concentrates”) are different. The concentrations of different anionic species were measured by ion chromatography using conductivity detection. The results show clear differences of anion concentrations and patterns between samples from different uranium mines. Besides this, differences between sampling campaigns in a same mine were also observed indicating that the uranium ore is not homogeneous in a mine. These within-mine variations, however, were smaller than the between-mine variations.     

Determination of cholride in natural and potable water samples byturbidimetric descrete-sample automatic analysis.

The reduction of the uranyl-mellitate complex at the dropping mercury electrode has been studied in aqueous and dimethyl sulfoxide solution. In aqueous solution, besides the reduction waves of the uranyl-mellitate complex, corresponding to the reduction of U(VI) to U(V), and of U(V) to U(III), an adsorption wave and a catalytic hydrogen wave were obtained; the species formed below pH 4.0 was UO₂(H₃A)^- and above pH 4.0 was UO₂(OH)(H₃A)^2-. In dimethyl sulfoxide solution, two well-defined waves were observed; the first wave is due to reduction of a uranyl-mellitate-DMSO complex, and the second to reduction of mellitic acid. The species involved are UO₂(DMSO)₆²⁺ below pH 2.2 and UO₂(H₃A)(DMSO)₅^-1 above pH 2.2. The activation energies of the reduction process were determined.     

New possibilities of energy-dispersive X-ray fluorescence technique in the analysis of potable water

The article considers specific features of schemes of X-ray fluorescence analysis of liquid samples in the geometry of thick layers and in thin layers using the X-ray optics scheme with total internal reflection. A scenario is proposed for the analysis of liquid samples in thin layers using a simple X-ray optics scheme lowering the detection limits 1000-fold in comparison with the traditional scheme in thick layers. The internal standard method is implemented to improve the reproducibility of the results. The proposed scenario was tested in the analysis of potable water.     

The spectrophotometric determination of arsenic in sea water,potable water and effluents

Procedures are described for the determination of arsenic in sea water, potable waters and effluents. The sample is treated with sodium borohydride added at a controlled rate. The arsine evolved is absorbed in a solution of iodine and the resultant arsenate ion is determined photometrically by a molybdenum blue method. The time required for a complete analysis is about 90 min, but of this only 15 min is operator time. For sea water the range, standard deviation, and detection limit are 1–4 μgl^-1, 1.4 % and O.14 μg l^-1, respectively; for potable waters they are 0–800 μg l^-1, about 1 % (at 20μg l^-1 level) and 0.5μg l^-1, respectively. Silver and copper cause serious interference at levels of 0.5 mgl^-1, and nickel, cadmium and bismuth interfere at concentrations of a few tens of mg l^-1; however, these elements can be removed either by preliminary extraction with a solution of dithizone in chloroform or by ion exchange. Arsenic present in organo-arsenic compounds is not directly determinable, but can be rendered reactive either by photolysis with ultraviolet radiation or by oxidation with permanganate or nitric—sulphuric acid mixture. Arsenic(V) can be determined separately from total inorganic arsenic after extracting arsenic(III) as its pyrrolidine dithiocarbamate into chloroform.     

Anion chromatography using on-line recycled eluents

Non-suppressed anion chromatography, using on-line recycled eluents, was investigated. Cations and anions from samples were excluded from the eluents using a mixture of strongly acidic cation-exchange resins and strongly basic anion exchange resins in the eluent reservoir. This exclusion was performed after determination of the anions in the non-suppressed anion chromatography, and the eluents were then recycled on-line. The performance of consecutive determinations was evaluated from the relative standard deviation (RSD) of peak heights and retention times of chloride, bromide, nitrite, nitrate, and sulfate ions, with a concentration of 3 microg ml(-1) each, compared to that of normal anion chromatography. Over 50 consecutive determinations could be achieved with an eluent volume of only 200 ml for a 100 microl sample volume. Almost all the RSD values for retention time, and peak heights of these anions, were smaller than 3%. Over fifty consecutive determinations of chloride, nitrate, and sulfate ions in a river water sample could be achieved with an eluent volume of only 100 ml. All the RSD values for retention time and peak heights of these anions were smaller than 3%. The eluent volume could be decreased to one tenth of that used in normal anion chromatography. The performance of the anion chromatography, using on-line recycled eluents, was the same as that for normal anion chromatography under the same conditions.     

Anion chromatography on hydroxyethyl methacrylate-based sorbents

The selectivity of sorbents plays an important role in the design of ion chromatographic separations. The selectivity of the hydroxyethylmethacrylate-based sorbent Tessek Separon HEMA-S 1000 Q-L was compared with those of other commonly used sorbents and the role of the eluent charge was investigated. The selectivity of this sorbent was found to be satisfactory for most commonly used ion chromatographic detection modes, including indirect photometry and both suppressed and non-suppressed conductivity detection.     

Interfacing gradient elution ion-exchange chromatography and low-angle laser light-scattering photometry for analysis of proteins.

Molecular weights (MWs) of different proteins were determined by interfacing gradient elution ion-exchange chromatography and low-angle laser light-scattering photometry (IEC-LALLS). A high-performance strong cation-exchange column was used to elute proteins using fast (5 min) and conventional (15-30 min) gradients. The eluted proteins were characterized on-line by determining their MWs using LALLS. The specific refractive index (RI) increment (dn/dc) and the RI of the solvent used over the gradient range were determined off-line and used to calculate the absolute weight-average MWs. Four proteins, ribonuclease A, alpha-chymotrypsinogen A, trypsinogen and beta-lactoglobulin A (beta-LACT) were studied. Accurate MWs were obtained for all the proteins using fast and conventional gradients, except for beta-LACT, which aggregated as a function of the gradient employed. The degree of aggregation of beta-LACT increased as the rapidity of the gradient was increased over a fixed gradient range. This study indicated that it is possible to separate and characterize proteins rapidly using IEC-LALLS.     

Simultaneous screening of estrogens,progestogens, and phenols and their metabolites in potable water and river water by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry

In this study, a method employing ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) was developed to simultaneously screen for 36 endocrine-disrupting chemicals (EDCs; e.g., estrogens, progestogens, phenols, and their metabolites) both in potable and river water. From the selected compounds, 21 target compounds, for which reference standards were available, were used as model compounds for method development and optimization. The other target compounds, for which reference standards were unavailable, were investigated in post-target analysis on the basis of their theoretical molecular masses. The solid-phase extraction and chromatographic separation steps were optimized. For this method, limits of detection for the target compounds were less than 0.72 ng L^? 1, and the overall recoveries varied between 46% and 134% with relative standard deviations ranging from 7% to 35%. The mass errors between theoretical and experimental mass for all resulting precursor and characteristic fragment ions ranged from ? 1.9 to 2.8 mDa. The method developed was successfully used to analyze the composition of potable and river water in Shanghai City; in addition, some compounds of interest (estriol, estrone, and bisphenol A) were identified accurately. Further, a post-target analysis was performed and an estrogen metabolite was hypothesized in the water samples due to the excellent sensitivity of the method in full-spectrum acquisition mode and the valuable accurate mass information in MS and tandem MS mode. Therefore, UPLC-Q-TOF-MS has proven to be a powerful technique for wide-scope screening and identification of relevant EDCs in environmental water sources.     

Anion dependent redox changes in iron bis-terdentate nitroxide {NNO} chelates

The reaction of [Fe(II)(BF(4))(2)]·6H(2)O with the nitroxide radical, 4,4-dimethyl-2,2-di(2-pyridyl) oxazolidine-N-oxide (L(?)), produces the mononuclear transition metal complex [Fe(II)(L(?))(2)](BF(4))(2) (1) which has been investigated using temperature dependent susceptibility, Mo?ssbauer spectroscopy, electrochemistry, density functional theory (DFT) calculations, and X-ray structure analysis. Single crystal X-ray diffraction analysis and Mo?ssbauer measurements reveal an octahedral low spin Fe(2+) environment where the pyridyl donors from L(?) coordinate equatorially while the oxygen containing the radical from L(?) coordinates axially forming a linear O(?)··Fe(II)··O(?) arrangement. Magnetic susceptibility measurements show a strong radical-radical intramolecular antiferromagnetic interaction mediated by the diamagnetic Fe(2+) center. This is supported by DFT calculations which show a mutual spatial overlap of 0.24 and a spin density population analysis which highlights the antiparallel spin alignment between the two ligands. Similarly the monocationic complex [Fe(III)(L(-))(2)](BPh(4))·0.5H(2)O (2) has been fully characterized with Fe-ligand and N-O bond length changes in the X-ray structure analysis, magnetic measurements revealing a Curie-like S = 1/2 ground state, electron paramagnetic resonance (EPR) spectra, DFT calculations, and electrochemistry measurements all consistent with assignment of Fe in the (III) state and both ligands in the L(-) form. 2 is formed by a rare, reductively induced oxidation of the Fe center, and all physical data are self-consistent. The electrochemical studies were undertaken for both 1 and 2, thus allowing common Fe-ligand redox intermediates to be identified and the results interpreted in terms of square reaction schemes.     

Trace analysis of N-formylmorpholine in hydrocarbons and water by gas-liquid chromatography

Summary N-Formylmorpholine, which is a solvent used in the extraction of benzene, toluene and xylenes extraction from petroleum feedstocks, is determined in trace amounts in water and in aromatic hydrocarbons by gas-liquid chromatography using two stationary phases. Traces of N-formylmorpholine in hydrocarbons was determined on a column packed with 2.3% Bentone 34+4.6% DEGA on Chromosorb W AW treated with 1% KOH. Traces of N-formylmorpholine in water was determined on 20% SE-30 on Chromosorb W AW. The developed methods were examined and proved to give quantitative results.     

Anion exchange silica monolith for capillary liquid chromatography

An anion exchange monolithic silica capillary column was prepared by surface modification of a hybrid monolithic silica capillary column prepared from a mixture of tetramethoxysilane (TMOS) and methyltrimethoxysilane (MTMS). The surface modification was carried out by on-column copolymerization of N-[3-(dimethylamino)propyl]acrylamide methyl chloride-quaternary salt (DMAPAA-Q) with 3-methacryloxypropyl moieties bonded as an anchor to the silica surface to form a strong anion exchange stationary phase. The columns were examined for their performance in liquid chromatography (LC) and capillary electrochromatography (CEC) separations of common anions. The ions were separated using 50 mM phosphate buffer at pH 6.6. Evaluation by LC produced an average of 30,000 theoretical plates (33 cm column length) for the inorganic anions and nucleotides. Evaluation by CEC, using the same buffer, produced enhanced chromatographic performance of up to ca. 90,000 theoretical plates and a theoretical plate height of ca. 4 μm. Although reduced efficiency was observed for inorganic anions that were retained a long time, the results of this study highlight the potential utility of the DMAPAA-Q stationary phase for anion separations. Figure Micro-LC performance evaluation of a strong anion exchange silica monolith column, 100H-MOP-DMAPAA-Q, 33 cm in length, with a mobile phase of 50 mM phosphate buffer, pH 2.8; linear velocity: u = 1.8 mm/s; UV-Vis detection at 254 nm. Sample solution (5 mg/mL of each component, 4 mL) was injected in split flow injection mode at a split ratio of ca. 1:1900 with a pump flow rate of 1.5 mL/min     

Natural mineral sorbents for chemical and microbiological purification of potable water

The role of a number of rocks (shungite, glauconite fossil rock, flint) in a chemical and microbiological purification of water was estimated. On the basis of a shungite-dolomite module a simple method for a widescale manufacture of chemically and microbiologically pure potable water with conditionated content of mineral matters was developed.     

Determination of cyclamate by high-performance liquid chromatography with indirect photometry

Most artificial sweeteners have been determined by high-performance liquid chromatography, but not cyclamate. We propose a simple method using standard equipment without any chemical reaction involving the cyclamate ion by applying the technique of indirect photometry. Saccharin, dulcin and aspartame may also be determined, if present.     

Anion effects in the pyrolysis-gas chromatography of quaternary phosphonium compounds

Pyrolysis-gas chromatography has been used to investigate the thermal decomposition of quaternary phosphonium salts having oxygen-containing anions. The nature of the anion influences both the temperature of decomposition and the nature of the products, and this is interpreted as evidence for the operation of a dual mechanism for the pyrolysis process.     

EAL interlaboratory comparison Wa1 – Testing of potable water

 The accreditation of laboratories has emphasized the use of interlaboratory comparisons as a tool to monitor the comparability and accuracy of results laboratories produce. An interlaboratory comparison for water laboratories was organized among European Cooperation for Accreditation (EA) member countries; 30 laboratories, 7 of which were not accredited, from 14 European countries participated in this intercomparison. All the laboratories were chosen by the appropriate national accreditation bodies, with the instruction to select as participants those laboratories which act as national reference laboratories in this field. About 90% of the data collected was considered satisfactory after statistical treatment. Non-accredited laboratories performed as well as accredited laboratories. The laboratories were asked to take corrective action and report the corrections to the accreditation bodies. A great variation in the reported uncertainties of the results was observed. There seems to be a need to organize EA interlaboratory comparisons for national reference laboratories analysing water. It is obvious that even reference laboratories need training in how to estimate the uncertainty of results. Received: 22 July 1998 · Accepted: 21 September 1998