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     

Spectrophotometrie determination of microgram quantities of hexavalent uranium

Summary A method is presented for the spectrophotometric determination of microgram amounts of hexavalent uranium by means of the azodyes Monochrome Black Blue G und Diamond Black PBB respectively.These two azodyes react with uranyl ions in an acetate buffered hydrochloric acid-methanolic medium under formation of colored chelates. 10 or 20 g uranium(VI)/10 ml measuring solution can still be determined with relatively high accuracy.

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Zusammenfassung Es wird eine Methode zur spektrophotometrischen Bestimmung von Mikrogrammengen Uran(VI) mittels der Azofarbstoffe Monochromschwarzblau G bzw. Diamantschwarz PBB angegeben. Diese beiden Azofarbstoffe reagieren mit Uranylionen in acetatgepuffertem salzsauermethanolischem Medium unter Bildung gefärbter Chelate. 10 bzw. 20 gUran(VI)/10ml Meßlösungkönnennoch mitrelativ hoher Genauigkeit bestimmt werden.

     

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.     

Spectrophotometric determination of microgram amounts of platinum

2-Ethyl-10-[3-(dimethylamino-2-methyl)propyl]phenothiazine hydrochloride (ethylisobutrazine hydrochloride) forms an orange-red complex with platinum(IV) at room temperature (26 ± 2 °C) in hydrochloric acid-sodium acetate buffer medium containing copper(II) ions. The complexation is complete within 10 min. The complex exhibits an absorption maximum at 529 nm with a molar absorptivity of 1.90 × 10⁴ liters mol^?1 cm^?1. Beer's law is obeyed over the concentration range 0.4–7.8 ppm of platinum. A 50-fold molar excess of the chromogenic reagent is necessary for the development of maximum color intensity. Job's method of continuous variation, the molar-ratio method, and the slope-ratio method indicate a 1:1 composition for the complex. The effects of pH, time, temperature, reagent concentration, order of addition of reagents, and interference of various ions are reported. The reagent has also been used successfully for the determination of platinum in minerals and alloys.     

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.     

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.     

Spectrophotometric determination of microgram amounts of chlorpromazine with chloranil

A simple spectrophotometric method for the determination of small amount of chlorpromazine has been developed. The reaction of chloranil as π-acceptor reagent with chlorpromazine was studied. The method is rapid, simple, and relatively sensitive and precise (RSD 1.8%). Beer's law was followed within the approximate concentration range of 50–900 μg in a final volume of 25 ml. Negative deviation was abserved beyond these limits. The general analytical and physical parameters were also established.     

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.     

Spectrophotometric determination of microgram amounts of ampicillin with chloranil

Ampicillin trihydrate (12.5–750 μg) is determined spectrophotometrically using chloranil as π-acceptor at pH 9. The method is relatively accurate (with a recovery of 100 ± 1.0%) and precise (RSD ⩽ 1.7%) and can be used successfully for capsules and ampoules.     

Spectrophotometric determination of submicro quantities of Ajmaline

A spectrophotometric method for the determination of 5–100 μg samples of ajmaline is described. Ajmaline gives a red colour with concentrated nitric acid, which is measured at 510 mμ after a definite time interval. The limits of interference from serpentine and ajmalicine are given. The method can be applied directly for the estimation of ajmaline in pharmaceutical preparations.     

Spectrophotometric determination of microgram amounts of amino acids with chloranil

Amino acids form molecular complexes with chloranil at pH 9.0 having apparent molar absorptivities at 350 nm ranging from 4,000 to 28,000. A spectrophotometric method for the determination of μg amounts of amino acids is described, based on such complex formation. There is no interference from urea and only a weak interference from ammonium ions.     

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.

     

Spectrophotometric determination of microgram amounts of aromatic aldoximes with chloranil

Benzaldoxime and its p-hydroxy, methyl, chloro and nitro derivatives (50–500 μg) are determined by using chloranil as a π-acceptor at pH 9. The method is simple, precise (r.s.d. <3%) and accurate (±2%).     

Spectrophotometric determination of rhenium using 2-pyridyl thiourea

The reagent 2-pyridyl thiourea produces a reddish brown complex with rhenium in hydrochloric acid medium in the presence of tin(II) chloride. The complex shows absorption maxima at 405 nm, obeys Beer's law for a range of 1–16 ppm of rhenium. The sensitivity and molar absorptivity is found to be 0.0115g cm^–2 and 1.603×10⁴ 1 mol^–1 cm^–1 respectively showing an improvement over other sulphur-nitrogen bearing ligands. Composition found by Job's and mole ratio method, indicates that the complex contains metal and reagent in the ratio 12. Stability constant and stepwise formation constants of the complex have been evaluated by Harvey-Manning's method (logK _overall=8.825), Leden's method (logK _overall=8.3096), Rossotti-Rossotti's method (logK _overall=8.653) and Yatsimirskii's method (logK _overall=8.740). The relative error per 1% absolute photometric error is found to be 2.7%.