The determination of nitrite and nitrate by the ring-oven technique

Determinations of nanogram amounts of nitrite and nitrate individually and together, based on a variation of the ring-oven technique, are described. In the “segment technique” used, a stable standard scale is not necessary. Interferences have been studied. Nitrite in sausages can be determined.     

Colorimetric determination of uranium(VI)

A new, very sensitive reagent is proposed for the colorimetric determination of uranium(VI), namely 1-phenyl-3-methyl-4-(3'-carboxy-4'-hydroxyphenyl-azo)-pyrazol-5-one.     

Semiquantitative determination of ajmaline by the weisz ring-oven technique

Ajmaline has been determined semiquantitatively with p-dimethylaminobenzaldehyde as reagent, with an error of +/-2%.     

Synergistic extraction and separation studies of uranium(VI)

A method is described for the extractive separation and spectrophotometric determination of uranium(VI) from an aqueous solution of pH 5.0–7.0 using benzoylacetone (bzac) and pyridine (py) dissolved in toluene as extractants. The extracted species are UO₂(bzac(₂·2py. The method provides separation of uranium(VI) from lanthanum(III), samarium(III), neodymium(III), cerium(III) and thorium(IV). The method is precise, accurate, fast and selective.     

Spectrophotometric determination of uranium(VI) with benzoylacetanilide

Ohne Zusammenfassung

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Use of complex forming substitution reactions for the selective enthalpiometric determination of cations and anions

     

Solvent extraction and spectrophotometric determination of uranium (VI)

Summary Solvent extraction of uranium-sodium diethyldithiocarbamate with ethylmethyl ketone and separation from titanium, zirconium, thorium, lanthanum and cerium has been described. It has been found that 11.75 to 47.00 mg of uranium can be extracted from a binary mixture containing 4.78 to 19.04 mg of titanium, 9.12 to 36.48 mg of zirconium, 116.0 to 460.0 mg of thorium, 6.95 to 27.8 mg of lanthanum or 7.06 to 28.24 mg of cerium at pH 3.0. The pH range between which the separations may be carried out successfully is 2.0 to 3.5. The following cations interfere in the separations: Cu^II, Fe^III, Co^II, Bi^III, Ni^II, Cr^VI, Te^IV, Se^IV, Ag^I, Hg^II, As^III, Sn^IV, Pb^IV, Cd^II, Mo^VI, Mn^II, V^V, Zn^II, In^III, Tl^I, W^VI, Os^VIII and Nb^V.

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Zusammenfassung Uran kann durch Extraktion als Diäthyldithiocarbamidat mit Methyläthylketon von Ti, Zr, Th, La oder Ce getrennt werden. Der günstigste pH-Bereich liegt zwischen 2,0 und 3,5. Die Trennungen wurden mit folgenden Mengen durchgeführt: U (11,75–47,00 mg); Ti (4,78 bis 19,04 mg), Zr (9,12–36,48 mg) Th (116,0–460,0 mg), La (6,95–27,8 mg), Ce (7,06–28,24 mg). Folgende Ionen verursachen Störungen: Cu^II, Fe^III, Co^II, Bi^III, Ni^II, Cr^VI, Te^IV, Se^IV, Ag^I, Hg^II, As^III, Sn^IV, Pb^IV, Cd^II, Mo^VI, Mn^II, V^VI, Zn^II, In^III, Tl^I, W^VI, Os^VIII sowie Nb^V.

     

Fluorescence determination of trace amounts of uranium(VI) in various materials by a repetitive laser technique

A laser-induced fluorescence method (LFM) is described for determination of trace amounts of uranium(VI), with a detection limit of 4 x 10(-11) g/ml. A repetitive pulsed laser, time discrimination and an averaging technique are used. The optimum time discrimination is obtained when the uranyl ion is complexed with phosphoric acid or sodium polysilicate. LFM does not need a preconcentration step or separation of uranium from interfering elements. The time needed for analysis is only 1-2 min.     

Extraction-spectrophotometric determination of uranium(VI) with PAR and N-octylacetamide

A new and simple method for selective spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol (PAR) and N-octylacetamide into benzene over pH 7.0–9.0 is described. The molar absorptivity of the complex with 9 different amides is in the range of (0.40–3.2)·10⁴ 1·mol^–1·cm^–1 at the absorption maximum. Out of these, the most sensitive compound N-octylacetamide (OAA) was chosen for detailed studies in the present investigation. The detection limit of the method is 0.008 g U·ml^–1. The system obeys Beer's law in the range of 0–5 g U·ml^–1. The method is free from interferences of most of the common metal ions except vanadium(V) and copper(II), which are masked by proper masking agents. The composition of the complex is determined by curve-fitting method. The method has been applied for the recovery of the metal from rock samples and synthetic mixtures.     

Extraction and spectrophotometric determination of uranium(VI) withN-phenylcinnamohydroxamic acid

Uranium(VI) reacts withN-phenylcinnamohydroxamic acid to form an orange-yellow complex in the pH range 5.5–8.5. The orange-yellow complex, having the composition of 12 (metal:ligand), is quantitatively extractable into ethyl acetate. The spectrum of the complex exhibits a maximum absorption at 400 nm with a molar absorptivity of 6500 M^–1·cm^–1. The coloured system obeys Beer's law in the concentration range 2–40g·ml^–1 of uranium(VI). The photometric sensitivity of the colour reaction is 0.037 g·cm^–2 of uranium(VI). Most of the common ions do not interfere and the method has been found to be simple, precise, and free from the rigid control of experimental conditions. The method has been applied to the determination of uranium in synthetic matrices and potable water.     

Spectrophotometric determination of uranium(VI) with 3-thianaphthenoyltrifluoroacetone

Summary Two visible spectrophotometric methods are described for the determination of uranium(VI) with 3-thianaphthenoyltrifluoroacetone at aph of 6.0. The effect due toph, time, solvents, reagent concentration and diverse ions are reported. Beer's law is obeyed in both cases and the molar extinction coefficients at 408 and 446 nm are 1.7·10⁴ and 2.3·10³ respectively.

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Zusammenfassung Zwei spektrophotometrische Methoden zur Bestimmung von U(VI) mit 3-Thianaphthenoyltrifluoraceton bei ph 6,0 wurden beschrieben. Der Einfluß vonph, Zeit, Lösungsmitteln, Reagenskonzentration und verschiedenen Fremdionen wurde angegeben. Das Beersche Gesetz wird in beiden Fällen befolgt. Der molare Extinktionskoeffizient bei 408 bzw. 446 nm beträgt 1,7 · 10⁴ bzw. 2,9 · 10³.

     

Optode for uranium(VI) determination in aqueous medium

A quantification procedure of trace elements during colloid size fractionation was developed and validated. This procedure is based on the hyphenation between Asymmetrical Flow Field-Flow Fractionation (As-Fl-FFF) and Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The optimisation of the procedure was performed on a soil leachate spiked with six trace elements selected for their environmental and health impact (As, Cd, Sb, Se, Sn and Pb). The elements in the spiked sample were on-line monitored during the fractionation. The validation was carried out by comparison with a second off-line quantification procedure based on fraction collection and total element analysis by ICP-MS. This off-line one was previously validated using reference materials. Finally, the analytical performances of the two procedures were compared.     

Determination of isonicotinic acid hydrazide (isoniazid) by the weisz ring-oven technique

A simple precise method is described for the determination of isonicotinic acid hydrazide (isoniazid) alone, and in mixtures with aspirin, paracetamol and streptomycin, by reaction with vanillin in the Weisz ring-oven technique; 0.1–15 μg of isoniazid can be determined with errors of 2–2.7%.     

Spectrophotometric study of the complexation equilibria of uranium(VI) with 1,4-bis(4′-methylanilino)anthraquinone and determination of uranium(VI)

The reaction of U(VI) with 1,4-bis(4′-methylanilino)anthraquinone (quinizarin green) in water-dimethylformamide medium was investigated spectrophotometrically. The complexation equilibria in solution were demonstrated. The study of the reaction in presence of equimolar concentrations or in solutions containing metal or ligand excess gave evidence for the formation of complexes with stoichiometric ratios of UO₂:L = 1:1 and 1:2 in dependence on the pH of the medium. Their thermodynamic stabilities and the values of their molar absorption coefficients were determined. The optimum conditions for spectrophotometric determination of U(VI) with this reagent were found.     

A new volumetric method for the determination of uranium(VI)

Summary A new volumetric method for the estimation of uranium(VI) salt based on its photoreduction in the presence of diethyl ether has been developed. The recommended procedure consists of exposing uranium(VI) solution in about 1 N sulphuric acid solution with an excess of saturated aqueous ether solution in a glass vessel to the light from a Phillips repro lamp or sun light for 1 hour. The uranium(IV) salt formed is estimated by titration with a standard solution of sodium vanadate.The reduction does not proceed to uranium(III) stage under any conditions of exposure. Fluoride, phosphate, arsenate and perchlorate are not found to interfere either with the photochemical reduction or with the subsequent oxidimetric titration. But chloride and bromide ions markedly inhibit the photochemical reaction.     

Separation and determination of uranium(VI) with calixarene hydroxamic acids

A new calixarene hydroxamic acid, 5,11,17,23-tetra-(N-p-chlorophenyl hydroxamate c-phenyl-25,26,27,28-tetrahydroxycalix[4]arene (CPCHA) was synthesized and used for the extraction and spectrophotometric determination of uranium(VI). The molar absorptivity of the uranium(VI)-CPCHA-thiocyanate complex was 9.9·10³ 1·mol^–1·cm^–1 at 436 nm. The system obeyed Beer's law in the range of 1.78–23.1 ppm of uranium. The uranium(VI)-hydroxamate-ethyl acetate complex was directly aspirated for graphite furnace atomic absorption spectrometry measurements (GFAAS) which increased the sensitivity by about a factor of fifty. Uranium was determined in various standard and environmental samples.     

Automated determination of uranium(VI) in seawater using on-line preconcentration by coprecipitation

An automated method is developed for the spectrophotometric determination of nanoamounts of uranium(VI) with Arsenazo III using online preconcentration by the coprecipitation of the uranium complex of the reagent with organic coprecipitants. The collector was an Arsenazo III ion pair with organic cations poorly soluble in water. The concentrate was separated by filtration through a cellulose fiber membrane and dissolved in a flow of an organic solvent; the analytical signal was recorded as the output peak. The developed method is characterized by simplicity, sufficiently high sensitivity, high throughput and rapidity, and can be used for the selective determination of uranium(VI) in complex liquid matrices. The detection limit is ～0.01 ng/mL (3s, n = 5, P = 0.95). The throughput of the method is 150 samples per hour.