Extraction of naphtholsulfonic acids from aqueous solutions with the use of a rotating concentrating unit and their photometric determination in the back extract

A new concentrating unit is proposed for the extraction of naphtholsulfonic acids; the unit is a ferromagnetic (steel) rod in a polyethylene or glass case coated with a mixture of cetyl alcohol with trioctylamine N-oxide. The rod is immersed in an analyzed solution and rotated in an alternating magnetic field (solid-phase extraction). The extraction-sorption characteristics of naphtholsulfonic acids were calculated, and a procedure was developed for their selective photometric determination in back extracts.     

聚乙二醇双水相萃取光度法测定镍

用水溶性高聚物、表面活性剂及有机物与无机盐形成的双水相体系萃取分离色素、蛋白质及测定金属离子已有报道[1-5].     

Extraction of mercury from aqueous iodide solutions by trilaurylamine N-oxide and its subsequent determination by atomic absorption spectrometry

A solvent extraction technique using 0.01M solution of trilaurylamine N-oxide in benzene as extractant has been used to concentrate mercury efficiently from water solutions with or without the presence of 0.02M KI in weakly acidic media. In addition to unmodified aqueous solutions, mercury can be extracted quantitatively from aqueous iodide solutions that are up to 1M in HCl, H₂SO₄, and HNO₃ in a single equilibration. Distribution coefficients and separation factors of several elements relative to mercury(II) are reported for media that contain 0.1 M HCl and 0.02M KI. The reagent is superior to aliphatic amines and quaternary amines for the extraction of mercury from aqueous iodide solutions.     

Extraction of 1:1 electrolytes from aqueous solutions by resins containing dibenzo-18-crown-6 as anchor groups

The electrolyte concentration dependence of the distribution ratio of 1:1 electrolytes between resins containing dibenzo-18-crown-6 and water at 298 K was studied. The apparent equilibrium constants for the process taking place when the resin is equilibrated with aqueous solutions of different electrolytes are reported. The results obtained clearly reflect the influence of the anion on the extraction of cations by the resin containing the macrocyclic ligand.     

Extraction and preconcentration of selenium from aqueous solutions and its determination in water and hair samples by atomic-absorption spectrophotometry

Several organic solvents, including benzene, xylene, toluene, nitrobenzene, chloroform, carbon tetrachloride, chlorobenzene and high molecular-weight pyridines such as 4-(5-nonyl)pyridine, 2-hexyl-pyridine and benzylpyridine have been investigated as components of systems for the extraction and preconcentration of selenium from nitric acid solutions containing iodide. The results are discussed in terms of choice of reagents and the acid and iodide concentrations, and of several other parameters affecting the extraction. The utility of the method for separation of selenium from aqueous solution has been evaluated. The method has been used for preconcentration of trace levels of selenium from water and hair samples for determination by atomic-absorption spectrophotometry.     

Use of triphenylmethane dyes for the spectrophotometric determination of polymer flocculants in aqueous solutions

The interaction of anionic forms of triphenylmethane dyes (TPM) with cationic polymer flocculants (e.g., with polydiallyldimethylammonium chloride (PC)) yields inextricable ion pairs. This leads to a shift of absorption bands or a redistribution of their intensities in the TPM spectra and can be used for the spectrophotometric determination of microgram amounts of flocculants in aqueous solutions. Among 14 studied TPMs, erythrosine is the most promising dye. The corresponding procedure allows the determination of PC at a level of the maximum permissible concentration. To decrease the effect of impurities, the use of the standard addition method is recommended.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 3, 2005, pp. 278–283.Original Russian Text Copyright © 2005 by Antonova, Vershinin, Dedkov.     

The effect of electrolytes on the sensitivity of the thermal-lens determination in aqueous solutions

The effect of several common surfactants (SDS, Triton X-100, Brij-35, and Tween 80) as modifiers of thermooptical properties of aqueous solutions on parameters of the thermal-lens analytical determination of several model systems is studied. Selection criteria for the compositions of modified aqueous media for thermal-lens analytical trace determination are discussed. The increase in the metrological parameters of thermal-lens measurements in nonionic-surfactant solutions is comparable with that for organo-aqueous mixtures. A twofold decrease in the limits of detection compared to aqueous solutions observed in 2.5 wt % surfactant solutions is achieved.     

Mixed aqueous solutions as dilution media in the determination of residual solvents by static headspace gas chromatography

Static headspace (HS) sampling has been commonly used to test for volatile organic chemicals, usually referred to as residual solvents (RS) in pharmaceuticals. If the sample is not soluble in water, organic solvents are used. However, these seriously reduce the sensitivity in the determination of some RS. Here, mixed aqueous dilution media (a mixture of water and an organic solvent like dimethyl formamide, dimethyl sulfoxide or dimethyl acetamide) were studied as alternative media for static HS-gas chromatographic analysis. Although it has been known that mixed aqueous dilution media can often improve sensitivity for many RS, this study used a systematic approach to investigate phase volumes and the organic content in the HS sampling media. Reference solutions using 18 different class 1, 2 and 3 RS were evaluated. The effect of salt addition was also studied in this work. A significant increase in the peak area was observed for all RS using mixed aqueous dilution media, when compared with organic solvents alone. Matrix effects related to the mixed aqueous dilution media were also investigated and reported. Repeatability and linearity obtained with mixed aqueous dilution media were found to be similar to those observed with pure organic solvents.     

Ionic association in aqueous solutions of strong electrolytes

A more accurate calculation of relaxation effects obtained with the standard Debye-Hückel-Onsager model has been presented recently and is here applied to several aqueous 1:1 electrolytes. The variation of the standard deviation between calculated and observed equivalent conductivities withK _A leads to an ill-defined minimum; but, where data over a wide concentration range are available, the minimum corresponds to values of the contact distancea which approximate to estimates from ionic dimensions. It is therefore proposed that, although preciseK _A values from conductance cannot be determined, the most probable values are those associated with realistic estimates ofa. When data cover a limited concentration range, minimum standard deviations are often indeterminate or vary greatly for duplicate runs. It is shown that reasonable values ofK _A can be obtained from such data if comparison is made at estimated values ofa.Notation The symbols not defined in the text are the following b e ²/kTa for 1:1 electrolytes - e electronic charge - k Boltzmann gas constant - T absolute temperature - dielectric constant of solvent - –(3/2y)(_e0/₀)     

Thermochemical study of acid-base interactions in L-asparagine aqueous solutions

The heats of reactions between an L-asparagine solution and HNO₃ solutions were measured calorimetrically within different pH ranges at 298.15, 308.15, and 318.15 K and an ionic strength of 0.5, 1.0, and 1.5 (KNO₃ and LiNO₃). The heats of stepwise dissociation of L-asparagine were determined. The standard thermodynamic characteristics (Δ _r H ^o, Δ _r G ^o, δ _r S ^o, and ΔC _p ^⪧) of the acid-base interactions in aqueous solutions of the amino acid were calculated. A relationship between the thermodynamic characteristics of the dissociation of L-asparagine and its structure was considered.     

Extraction of ethylene glycol from aqueous salt solutions

A method is proposed for extracting ethylene glycol from aqueous salt solutions by dialysis through ion-exchange membranes, based on the Donnan exclusion of the electrolyte. Dialysis is performed in the continuous and batch modes. It is found that the batch mode of dialysis is more effective for extracting ethylene glycol from its aqueous salt solutions. The effect of the ionic form of the membrane on ethylene glycol fluxes is explained through computer simulation.     

On the use of azo dyes for the spectrophotometric determination of uranium and thorium in mixed solvents

Summary Solochrome Black 6 BN in an acetate buffered medium containing methanol reacts with U(IV) to give a blue complex which permits photometric determination with 5g U/ml to 100g U/ml.In the presence of zinc acetate, uranyl ion also may be spectrophotometrically determined by means of the same dye. From 2g U/ml to 40g U/ml may be determined with a relative error of less than ± 0.05.

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Zusammenfassung Es werden zwei Methoden zur spektrophotometrischen Bestimmung von Uran mittels Solochromschwarz 6 BN beschrieben. Dieser Farbstoff bildet mit U(IV) in acetatgepuffertem, methanolhältigem Medium einen blaugefärbten Komplex, der die Bestimmung von 5 bis 100g U/ml erlaubt.Mit demselben Farbstoff lassen sich auch 2 bis 40g U/ml in Lösungen von Uranylchlorid bestimmen.

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Résumé Le noir solochrome 6 BN en milieu tampon acétique contenant du méthanol réagit avec U-IV en donnant un complexe bleu qui permet le dosage photométrique de 5 g U/ml à 100 g U/ml.En présence d'acétate de zinc, on peut aussi doser l'ion uranyle par spectrophotométrie avec le même colorant. On peut doser de 2 g U/ml à 40 g U/ml avec une erreur relative inférieure à ± 0,05.