Accurate determination of microgram quantities of uranium by direct and differential polarography

Summary A procedure for the accurate determination of small amounts of pure uranium (5–1,000 g) by direct or comparative polarography is described. The accuracies obtainable for different total quantities are given.

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Zusammenfassung Direkte und differentielle polarographische Verfahren zur Bestimmung von kleinen Mengen Uran (5–1000 g) werden beschrieben und die für verschiedene Gesamtmengen erreichbaren Genauigkeiten angegeben.

     

Determination of microgram quantities of uranium in thorium

Uranium present in micro amounts in thorium is extracted with 5% tributyl phosphate in presence of EDTA at pH 2.5. Calcium nitrate is used as salting agent. Uranium is back-extracted with ammonium carbonate and determined fluormetrirically. Thoria samples containing as little as 0.4 p.p.m. of uranium have been analysed.     

Direct spectrophotometric determination of microgram quantities of copper in high purity uranium with oxaldihydrazide

Summary The possibility for the direct spectrophotometric determination of microgram quantities of copper in high purity uranium using oxal-dihydrazide-acetaldehyde reagent in ammoniacal medium was investigated. Uranium was complexed with ammonium citrate or ammonium carbonate.It was shown that copper can be determined with fairly good accuracy. At the copper concentration of 0,1 ppm and 1 ppm relative mean deviation in amounts to 7,38 and 0,94 respectively.The selectivity of the reaction is very high, the only interference being cobalt which when present in equal concentrations increases the absobance by about 5%.Thanks are due to Miss Kira Jovanovi for her help in taking the spectrophotometric measurements.     

Spectrophotometric determination of microgram quantities of indium in uranium and thorium metals and their salts

A method based on dithizone extraction and determination of indium in the range of 0 1 to l0 p p,m in reactor gracde uranium and thorium samples is described Sodium thiosulphatc is uscd as a, complexing agent for removing interference by lead and bismuth     

Spectrophotometric determination of thiourea in microgram quantities

Summary Copper(II) forms a stable colourless complex with thiourea. This property has been utilized to develop a Spectrophotometric method for the determination ofg quantities of thiourea. The complex absorbs in ultraviolet region and the determinations are carried out at 250 nm. The method permits the determination of thiourea from 10–60g with error not exceeding ± 1.0%.

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Zusammenfassung Kupfer(II) bildet mit Thioharnstoff eine farblosa Komplexverbindung, die sich auf Grund ihrer Absorption bei 250 nm zur spektrophotometrischen Bestimmung von Mikrogrammengen Thioharnstoff eignet. 10 bis 60g Thioharnstoff lassen sieh mit einem Fehler von höchstens ± 1,0% bestimmen.

     

The determination of microgram quantities of organic nitrogen

A method is descriibed for the determination of microgram quantities of nitrogen in a wide variety of materials. This method involves the Kjeldahl procedure for the conversion of nitrogen to ammonium or amine sulphate. Digestion of the sample with concentrated sulphuric acid and catalyst, and, if necessary, pretreatment with hydriodic acid and red phosphorus, are followed by steam-distillation into a dilute acid solution. The final determination depends on the reaction of ammonia, in a suitably buffered solution, with sodium hypobromite reagent, and measurement of the excess reagent by titration of the iodine liberated by it from acidified potassium iodide, with a standard $\text{N}\text{500}$ sodium thiosulphate solution, using sodium starch glycollate indicator.Since sample size is relatively unrestricted and the final titration can measure 5 micrograms of nitrogen, the sensitivity of the method is very high.Reference is made to existing sub-micro methodes which, although sensitive, are time-consuming and specific in application.     

The polarographic determination of microgram quantities of oxalic acid

A brief critical summary of possible methods for the determination of micro quantities of oxalic acid in solution is presented, and details are given of a satisfactory polarographic procedure for the determination of this material down to a level of 10 microg per ml in the final solution. This method involves the adjustment of the pH of the sample solution, followed by precipitation of the oxalic acid as europium oxalate. The excess europium is then determined polarographically. The method is applicable in the presence of 1M ammonium nitrate and in the presence of ammonium salts of other common acids. Iron and chromium interfere and must be absent.     

The determination of microgram quantities of sulphide in biological materials

Several methods for the estimation of microgram quantities of sulphide in biological material and enzymatic reaction mixtures were investigated- The optimum conditions for separation of sulphide by isothermal distillation are given. The formation of méthylène blue is recommended for the spectrophotometric determination of sulphide; modifications are described to improve the reliability and sensitivity of the method.     

New reagents for the colorimetric determination of microgram quantities of nitrite

Summary Two new reagents,N-(2-amino-phenyl) morpholine (I) andN-(2-amino-phenyl) piperidine (II), are used for determination of nitrite ion in acid solutions containing up to 20g NO₂ ^–/ml. The diazonium compound of (I) is sufficiently stable to enable measurement of absorption of light at 435 nm immediately after formation at room temperature or after standing in the dark.The reaction is sensitive to 0.05g NO₂ ^–/ml using a 1-cm light path.

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Zusammenfassung Zwei neue Reagenzien, N-(2-Aminophenyl)-morpholin (I) und N-(2-Aminophenyl)-piperidin (II) wurden für die Bestimmung des Nitritgehaltes saurer Lösungen unter 20g NO₂ ^–/ml herangezogen. Die Diazoniumverbindung von I ist hinreichend stabil zur Bestimmung der Absorption bei 435 nm unmittelbar nach ihrer Herstellung bei Zimmertemperatur oder nach Stehen im Dunkeln. Die Empfindlichkeit entspricht 0,05g NO₂ ^–/ml bei 1 cm Schichtdicke.

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Résumé On utilise deux nouveaux réactifs, la N-(amino-2 phényl) morpholine (I) et la N-(amino-2 phényl) pipéricline (II), pour doser l'ion nitrite en solutions acides contenant jusqu'à 20g NO₂ ^–/ml. Le composé diazonium de (I) est suffisamment stable pour permettre la mesure de l'absorption de la lumière à 435 nm, immédiatement après formation à la température ambiante ou après séjour à l'obscurité.La réaction est sensible à 0,05g NO₂ ^–/ml en utilisant un chemin optique de 1 cm.

     

Quantitative inorganic paper chromatography direct determination of nickel in microgram quantities

A method has been developed for the direct determination on filter paper of nickel, after Chromatographic separation of interfering elements. The sample is dissolved in ₃N hydrochloric acid and the solution is spotted on filter paper, together with standard solutions of nickel. After chromatographic development with a mixture of acetone, hydrochloric acid and acetylacetone, the nickel spot, which has scarcely moved, is made visible by spraying with a solution of rubeanic acid, and its reflectance is measured with a Beckman DU Spectrophotometer at 625 mμ. Most interfering elements have moved away because of their high R_F values. In the presence of large amounts of aluminiun, chromium, titanium or vanadium, a preliminary extraction of the nickel is necessary. Several technical alloys have been analyzed successfully by this method, for which only 0.045 ml of solution, containing 0.45–9 μg of nickel, are needed, although its precision is equal to that of the best colorimetric methods.     

Absorptiometric determination of microgram amounts of uranium with Rhodamine B

Uranium (VI) can be extracted as a complex with rhodamine B into a benzeneetherhexone solvent from a benzoate buffered solution. Optimum conditions for the colour development are defined, leading to a molar absorptivity of 102700 mmol^-1 cm² at 555 nm, the highest yet reported for a uranium complex. The determination of uranium in the range 0.02–3 μg/ml in nitrate samples is described. The relative standard deviation ranges from 20 to 0.6%. The interference of several ions is investigated.     

Colorimetric determination of microgram quantities of isonicotinic acid hydrazide (isoniazid)

Microchimica Acta - The orange yellow colour of the vanadium(V)-isoniazid complex measured at 420 nm (Filter No. 42) is utilized as the basis for the colorimetric determination of isoniazid in the...     

The determination of microgram quantities of fluoride: The use of the aluminium-chromeazurol-s complex

A spectrophotometric method for determining fluoride using the aluminium chromeazurol complex is described. Fluoride in solution free from interfering ions or obtained by distillation as hydrofluosilicic acid is determined by destruction of the complex, the amount destroyed being directly proportional to the fluoride present. The method will detect as little as 0.02 μg/ml of fluoride and with 0–20 μg in the final solution fluoride can be determined with an accuracy of ± 0.6 μg.     

The determination of microgram quantities of fluoride : The use of the aluminium-haematoxylin complex

This paper describes a method for the spectrophotometric determination of fluoride. The fluoride is separated from interfering ions by the standard method of distillation as hydrofluosilicic acid. The fluoride in this distillate is determined by its destruction of the aluminium-haematoxylin complex; the amount of complex destroyed which is directly proportional to the concentration of fluoride is measured spectrophotometrically using radiation of 5700 A. The method will detect down to 0.05 p.p.m. of fluoride on a 10 gram sample with precision of rather better than ± 10% with larger amounts of fluoride. references p. 368.     

The determination of microgram quantities of fluoride: The use of the aluminium-eriochromecyanin complex

A spectrophotometric method for determining fluoride using the aluminium-eriochromecyamn complex is described. Fluoride in solutions free from mterfering ions,or obtained by distillation as hydrofluosilicic acid is determined by its destruction of the complex, the amount destroyed being directly proportional to the fluoride content. The method will detect as little as 0.02 μg/ml of fluoride and with 0–20 μg in the final solution fluoride can be determined with accuracy of ± 0.6 μg.A preliminary study of the aluminium-eriochromecyanin-fluoride system, has been carried out and a tentative reaction mechanism suggested.     

Atomic absorption spectrophotometric determination of microgram quantities of copper in tea after solvent extraction

An atomic absorption spectrophotometric method is described for determining trace amounts of copper in tea. The method is based on the solvent extraction of the metal as tetraiodocuprate (I), from 2 M HCl solutions of tea samples which contain 12% (w/v) KI, into methylisobutyl ketone. The organic extracts, containing the ion-association complex of copper are atomized into an air-acetylene flame. The limit of detection is 1.14 micrograms g-1 Cu.