Colorimetric determination of molybdenum using sodium diethyldithiocarbamidate as reagent

Summary A method for the photometric estimation of molybdenum(V) by extraction of the complex formed with NaDDTC in 5 N HCl solution is discussed. The reduction of Mo(VI) to Mo(V) is achieved with hydrazine sulphate. The colour intensity of the chloroform extract of the complex is measured at 450 nm. Beer's law is obeyed up to 500 g/25 ml of molybdenum.

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Zusammenfassung Zur photometrischen Molybdänbestimmung wird der Komplex mit Diäthyldithiocarbamidat verwendet, der in 5 N salzsaurer Lösung gebildet und mit Chloroform extrahiert wird. Mo(VI) wird mit Hydrazinsulfat zur fünfwertigen Stufe reduziert. Die Messung erfolgt bei 450 nm; das Beersche Gesetz ist bis zu 500 g Mo/25 ml erfüllt.

     

Colorimetric determination of fluoride ion with a solid analytical reagent

A colorimetric procedure is proposed for the estimation of fluoride ions in μg range in aqueous samples. The method involves the use of a solid analytical reagent and exhibits an operational simplicity. The detection limit of 1 ppm in an aqueous sample is conveniently achieved in the direct application. The interfering ions are initially removed in an ion exchange step, which also serves as a concentration step for fluoride if present in low concentration.     

Colorimetric determination of capsaicin in capsicum fruits with the Folin-Ciocalteu reagent

Summary A colorimetric method for determination of capsaicin in capsicum fruits is described. The acetone or ethyl acetate extract (prepared at room temperature) is purified on a basic alumina (Brockmann Grade I) column and pure capsaicin is eluted with methanol-acetone-water (75251); the capsaicin content is determined after colour development with Folin-Ciocalteu reagent, the absorbance being measured at 760 nm. The method is reproducible and results are in good agreement with those obtained by existing methods.

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Zusammenfassung Eine kolorimetrische Methode zur Bestimmung von Capsaicin in Paprikafrüchten wurde beschrieben. Der bei Zimmertemperatur gewonnene Aceton-oder Essigesterextrakt wird in einer Säule aus basischem Aluminiumoxid (Brockmann I) gereinigt und das reine Capsaicin durch Farbreaktion mit Folin-Ciocalteu-Reagens und Messung bei 760 nm durchgeführt. Die reproduzierbaren Ergebnisse stimmen mit denen anderer Methoden gut überein.

     

Chlorpromazine hydrochloride as an analytical reagent : Colorimetric determination of micro quantities of gold

Chlorpromazine hydrochloride is proposed for the colorimetric determination of gold in acidic medium at 530 mμ. Comparatively large amounts of copper, silver, iron, lead, etc. can be tolerated. The colour is stable; Beer's law is obeyed over the range 0.5–8 mμ of gold per ml.     

Fluorimetric determination of boron with resacetophenone as a reagent

Summary A method has been developed for the fluorimetric determination of boric acid, which gives a blue fluorescence with resacetophenone in sulphuric acid or phosphoric acid medium. The method has the advantage that the reaction does not require much time, because the fluorescence intensity reaches its maximum immediately after mixing the reagents and does not also decrease with time. The intensity of fluorescence can be measured with a fluorimeter and the amount of boric acid determined from a calibration curve.     

Gravimetric determination of palladium with quinolinimide as a reagent

Summary Quinolinimide which is found to be a selective reagent for palladium forms a complex of the composition Pd(C₇H₃O₂N₂)₂. The reagent quantitatively precipitates palladium from solutions of p_H 0.5 to 2.5 in presence of common ions as well as platinium metals, except tin which, however, can be kept in solution by complexing with citric acid. The palladium complex being stable up to 307° C can be directly weighed.

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Zusammenfassung Chinolinimid wird als selektives Reagens für Palladium vorgeschlagen. Bei p_H-Werten zwischen 0,5 und 2,5 kann Palladium quantitativ in Form des Komplexes Pd(C₇H₃O₂N₂)₂ gefällt werden, wobei die meisten anderen Ionen, auch die der Platinmetalle, in Lösung bleiben. Zinn stört, kann aber mit Citronensäure maskiert werden. Der Palladiumkomplex ist bis 307° C stabil und kann direkt ausgewogen werden.

     

Colorimetric uranium determination with arsenazo

A rapid and sensitive method is described for the quantitative colorimetric determination of uranium(Vl). Masking agents such as EDTA, tartaric acid or thioglycerol make possible the determination of uranium in the presence of many foreign metal ions. If thorium is present, a preliminary extraction of uranium as the diethyldithiocarbamate is required.     

The determination of thiols with diphenylpicrylhydrazyl as a spectrophotometric reagent

Diphenylpicrylhydrazyl (DPPH), a stable, intensely purple free radical, is used as a reagent in the quantitative determination of various aromatic and aliphatic thiols by indirect spectrophotometric analysis. Plots of degree of reaction vs. time show that thiophenol and its derivatives react more quickly than aliphatic thiols with DPPH. Calibration plots are linear over the concentration range 0.05-3.00 x 10(-5)M thiol. The average relative error is in the range 1-2% and the absolute standard deviations range up to 0.50 x 10(-6)M.     

Colorimetric determination of piperazine with p-benzoquinone

Piperazine and its salts are reacted with aqueous alcoholic p-benzoquinone, buffered at pH 5.4, to give a coloured product with maximum absorption at 516nm. The piperazine base has a molar absorptivity of 0.96 x 10(4)l.mole(-1).cm(-1) and Beer's law is obeyed over the range 2-10 mug ml . When applied to three commercial preparations, the proposed method gave mean recoveries within 1% of those obtained by the official gravimetric method. The relative standard deviation was less than 1%.     

Selective complexometric determination of mercury with sulphite as indirect masking reagent

A complexo-titrimetric method for the determination of mercury(II) in the presence of other metal ions is described, based on the selective masking ability of sulphite ion towards Hg(II). Mercury in a given sample solution is initially complexed with a known excess of EDTA and the surplus EDTA titrated with zinc sulphate solution at pH 5.0–6.0 (hexamine), using xylenol orange (or methylthymol blue) as indicator. An excess of solid sodium sulphite is then added to decompose the Hg(II)-EDTA complex and the released EDTA is titrated with standard zinc sulphate solution. Reproducible and accurate results are obtained for 9.9–99 mg Hg with relative errors < 0.35% and standard deviations < 0.05 mg. The effects of various cations and anions are studied.     

Colorimetric determination ofm-aminophenol

Summary Potassium iodate reacts withm-aminophenol in presence of sulfuric acid to give pink violet color having 5g as visual limit of identification. The color reaction is specific form-aminophenol;o-, andp-aminophenol do not interfere if their amount does not exceed 10 and 70% respectively. This provides a new colorimetric method for the determination ofm-aminophenol in small quantities.

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Zusammenfassung Kaliumjodat reagiert mit m-Aminophenol in Gegenwart von Schwefelsäure unter Bildung einer rosavioletten Farbe mit einer Erfassungsgrenze von 5g. Die Reaktion ist spezifisch; o- und p-Aminophenol stören nicht, sofern nicht mehr als 10 bzw. 70% anwesend sind. Daraus ergibt sich ein neues kolorimetrisches Verfahren zur Bestimmung kleiner Mengen m-Aminophenol.

     

Selective determination of copper with pyridoin phenylhydrazone as chromogenic extraction reagent

Summary The synthesis, characteristics and analytical applications of pyridoin phenylhydrazone are described. It reacts with copper(I) to produce an orange 11 complex ( _max=450 nm,=2.1×10⁴l· mole^–1·cm^–1) in aqueous ethanolic solution; it behaves as a cuproin type reagent. The orange complex can be extracted into amyl alcohol ( _max=440 nm,=2.0×10⁴l·mole^–1·cm^–1), and used for the spectrophotometric determination of trace amounts of copper. Interferences have been investigated.

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Zusammenfassung Synthese, Eigenschaften und analytische Anwendung von Pyridoin-phenylhydrazon wurden beschrieben. Es reagiert mit Cu(I) unter Bildung eines orange gefärbten 11-Komplexes in wäßrig-alkoholischer Lösung ( _max=450 nm,=2,1×10⁴l·mol^–1·cm^–1); das Reagens verhält sich ähnlich wie Cuproin. Der erwähnte Komplex läßt sich mit Amylalkohol extra-hieren ( _max=440 nm,=2,0×10⁴l·mol^–1·cm^–1) und zur spektrophoto-metrischen Bestimmung von Kupferspuren benützen. Auftretende Störungen wurden angegeben.

     

The spectrophotometric and titrimetric determination of gold with ferroin as reagent

A spectrophotometric and a photometric titration method in a two-phase system for the determination of gold with ferroin is reported. Both methods are rapid and reproducible with an accuracy of ±1%. In the spectrophotometric determination Co²⁺, Cu²⁺, Ni²⁺ , Fe³⁺, Zn²⁺, Mn²⁺ and Cr³⁺ do not interfere with the determination of gold and Pt⁴⁺, Pd²⁺, Hg²⁺, Ir⁴⁺ and Os⁴⁺ can be tolerated up to a ratio of 1:1. The titrations can also be carried out in the presence of a number of diverse ions, e.g. Ni²⁺, Cu²⁺, Co²⁺, Fe³⁺, Zn²⁺, Cr³⁺, Mn²⁺, without interference; the platinum metals and Hg²⁺ cause interference but, by the use of the spectrophotometric procedure, this can be reduced.     

Colorimetric determination of thorium with Methylthymol Blue

Thorium forms with Methylthymol Blue (MTB) in alkaline medium (pH 9–10) a complex of the composition Th(MTB)₂, even in the presence of EDTA, which masks almost all metals against the reagent. This can be used for selective determination of traces of thorium (0.5–2.8 ppm) by measurement of the absorbance at 535 nm.     

Colorimetric determination of iron with meconic acid

Meconic acid, a suitable reagent for the colorimetric determination of ferric iron, is presented. The nature of the chemical behaviour of the complex has been studied. The reagent must be used in acid medium (pH = 1). When the observation is made in Nessler's cylinder the sensitivity is one part in 5.000,000; in spot-plate the limit of identification is 0.5 microgram at a limiting concentration of 1 :400.000. The colored complex obeys Beer's law over a useful range of iron concentration.     

Colorimetric determination of persulfate with alcian blue

Alcian blue buffered at pH 2.5 is oxidized by persulfate. The plot of optical density at 615 mμ vs. concentration of persulfate (within the range of 10 to 80 μg) is linear. The assay is not affected by bromate and iodate.     

Colorimetric determination of some sulphonamides with phenothiazine

Two simple and sensitive calorimetric procedures for determination of some sulphonamides with phenothiazine (thiodiphenylamine) are presented. One is based on reaction in aqueous alcohol solution in presence of hypochlorite, with direct measurement at 515 nm. The other is based on reaction in presence of copper(II) acetate at 70 degrees , extraction with chloroform and measurement at 515 nm. The method is applied to the determination of sulphonamides in pure and tablet form, with a coefficient of variation less than 2%.     

Flow-injection determination of nitrites based on their reaction with thiocyanates

A technique for the flow-injection determination of nitrites with spectrophotometric signal detection was developed and studied. Additionally, a combination of the developed technique with the on-line pre-concentration of low concentrations of nitrites in surface and potable waters was investigated. The technique is based on the reaction of nitrites with thiocyanates. The product of the analytical reaction (nitroso-S-thiocyanate) and its adducts with strong acids are stable in aqueous solutions, which is supported by quantum chemical calculations. It is shown that the reaction chosen is attractive for analytical applications, because it is highly selective. A decrease in the detection limit down to 1.5 ng/mL (3s) is achieved by combining FIA with on-line ion-exchange preconcentration. The technique developed is used for monitoring nitrites in natural and waste water. The throughput capacity is 300 samples per hour.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 3, 2005, pp. 323–330.Original Russian Text Copyright © 2005 by Kuznetsov, Zemyatova, Ermolenko.