Colorimetric determination of sinalbin

Summary Sinalbin (Sinapinp-hydroxybenzylglucosinolate) is present in white mustard seed(sinapis alba) and on enzymatic hydrolysis liberates a sharp, hot, pungent and flavoury compound,p-hydroxybenzyl isothiocyanate (p-HBI). A new sensitive colorimetric method has been developed in which thep-HBI is reacted with sodium hydroxide to givep-hydroxybenzyl alcohol and sodium thiocyanate. The thiocyanate is converted into cyanogen bromide by reacting it with bromine. The cyanogen bromide is then treated with pyridine—benzidine reagent to give a red colour which has an absorption maximum at 518 nm. The red complex solution obeys Beer's law over the concentration range 0.1–0.5 g of SCN per ml of the solution. One mole of sinalbin gives rise to one mole of thiocyanate ion. Recovery is 90%.

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Zusammenfassung Sinalbin (Sinapin-p-hydroxybenzylglucosinolat) ist ein Inhaltsstoff des Samens von weißem Senf (Sinapis alba) und bildet bei enzymatischer Hydrolyse eine scharf schmeckende, würzig riechende Verbindung, p-Hydroxybenzyl-isothiocyanat (p-HBI). Ein neues kolorimetrisches Verfahren wurde entwickelt, das auf der Reaktion von p-HBI mit Natronlauge beruht, wobei p-Hydroxybenzylalkohol und NaCNS entstehen. Dieses wird mit Brom zu Bromcyan umgesetzt, das seinerseits mit Pyridin-Benzidin eine Rotfärbung mit dem Absorptionsmaximum bei 518 nm gibt. Die Lösung dieser roten Komplexverbindung folgt dem Beer'schen Gesetz von 0,1–0,5 g SCN^–/ml. Ein Mol Sinalbin entspricht einem Grammion Thiocyanat. Die Ausbeute beträgt etwa 90%.

     

Colorimetric determination of manganese

The colour developed, when freshly formed manganese dioxide dissolves in alkaline tellurate solution is found to be suitable for the colorimetric determination of manganese. The colour obeys Beer's law within the concentration range 1.886.10^-4 - 7.54.10^-4M. The colour is developed by oxidizing Mn(II) (in presence of 2.5M alkali) with the equivalent amount of H₂O₂ in the presence of 4 moles of telluric acid per mole Mn(II).     

Colorimetric determination of magnesium

From a critical study of the colorimetric determination of magnesium with titan yellow we concluded that: a. titan yellow must be present in excess; b. a mixture of glycerol and starch solution is satisfactory as protecting colloid; c. the influence of calcium becomes constant with concentrations 10 mg Ca⁺² per 100 ml; d. aluminium, iron, phosphate, ammonium and silica interfere; e. alkali-ions interfere when present in large quantities.The method is rapid and the accuracy is satisfactory and can be recommended for the determination of Mg⁺² in water and in silicates.     

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.     

Colorimetric determination of anionic detergents

Many types of anionic detergents can be determined colorimetrically by the action of the detergent on a protein-bromcresol purple complex. The amount of free dye liberated from the complex is proportional to the amount of detergent added between certain limits.     

Colorimetric determination of water in acetone

A colorimetric method utilising dithizone for the determination of water in acetone is described. The method is based on the change of color with water content, which is possibly due to keto-enol formation of the dithizone. Calibration curves at 608 nm are linear at low water concentrations ; the absorbance decreases with increasing water concentration. A detection limit of 0.02 g of water per 100 ml of solution was obtained. The method is applicable to the determination of water of hydration in metal salts that do not react with dithizone.     

Colorimetric determination of isonicotinic acid hydrazide

Summary Isonicotinic acid hydrazide reacts with catechol in alkaline medium to give a pinkish-orange color which obeys Beer's law. This color reaction is specific for isonicotinic acid hydrazide and is used for its determination in blood or urine. The visual limit of identification is 1 g/ml.

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Zusammenfassung Isonikotinsäurehydrazid reagiert in alkalischem Milieu mit Brenzcatechin. Dabei bildet sich eine Rosa-orange-Färbung, die dem Beerschen Gesetz entspricht. Diese Farbreaktion ist für Isonikotinsäurehydrazid spezifisch und für dessen Bestimmung in Blut und Harn geeignet. Die Nachweisgrenze liegt bei 1 g/ml.

     

Colorimetric determination of dimethoate or omethoate

A simple, sensitive and rapid colorimetric method is described for determining dimethoate [O,O-dimethyl-S-(N-methylcarbanoylmethyl)phosphorodithioate] and omethoate by an enzymatic method using pig liver acetone powder as enzyme source and p-nitrobenzenediazonium fluoroborate as the chromogenic reagent. This colorimetric method is more sensitive than non-enzymatic methods. Inhibition can be detected at ng levels and amounts ranging from 50 to 1000 ng of omethoate and from 1 to 10 mug of dimethoate can be estimated.     

Colorimetric determination of pyrazole in blood

Summary A colorimetric procedure has been developed whereby pyrazole may be determined in blood. The pyrazole is assayed as a reaction product with pentacyanoaminoferrate(III). The method is rapid, straightforward, and will detect levels of pyrazole down to 0.1mol in a total sample volume of 0.2 ml. There appears to be no interfering materials in the serum of normal animals.

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Zusammenfassung Eine kolorimetrische Methode zur Bestimmung von Pyrazol im Blut auf der Basis seines Reaktionsproduktes mit Pentacyanoaminoferrat(III) wurde ausgearbeitet. Sie eignet sich bis zur Größenordnung von 0,1Mol Pyrazol in 0,2 ml Probe. Im Serum normaler Tiere fanden sich keine die Bestimmung störenden Substanzen.

     

Colorimetric determination of carbon in titanium

A method is proposed for the colorimetric determination of carbon in titanium. In the method the sample is dissolved in a mixture of sulfuric and fluoboric acids, and nitric acid is added to dissolve the titanium carbide. The solution is boiled and filtered, and the yellow coloration from the nitrated organic complex is read with a spectrophotometer. A spectrophotometric study of the color was made. A comparison was made between the colorimetric determination of carbon in titanium and the colorimetric determination of carbon in steels. The proposed method is rapid and is readily adaptable to the determination of carbon in a large number of samples at one time. The procedure is designed for titanium containing up to 0.7 per cent. carbon. None of the elements encountered in “commercially pure” titanium metal interferes.     

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%.     

Colorimetric determination of boron in nitrate solutions

A method has been developed for the determination of microgram amounts of boron in nitrate solutions. Nitrate is destroyed with formic acid and sulphuric acid under reflux conditions. As much as 3 millimoles of nitrate are reduced completely by refluxing 1 ml of the nitrate solution with 1 ml of 88% formic acid for 15 minutes. Boron is determined by the carminic acid method after forming the colored complex in situ. This method has been applied to the determination of boron in uranyl nitrate solutions after extraction of uranium with tri-n-octylphosphine oxide dissolved in cyclohexane.     

Colorimetric determination of pyridoxine in pharmaceutical preparations

Summary The USP method for the determination of pyridoxine hydrochloride in pharmaceutical preparations has been modified to increase the stability of the colour, the speed of determination and the sensitivity. The reaction is carried out in propan-2-ol medium instead of water triethanolamine is used as the buffer, and iodine is used as oxidant when necessary. The colour is stable for about 45 min, the sensitivity of the reaction is greatly increased and the method takes only about a fifth of the time of the USP method.

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Kolorimetrische Bestimmung von Pyridoxin in pharmazeutischen Präparaten

Zusammenfassung Die USP-Methode zur Bestimmung von Pyridoxinhydrochlorid in pharmazeutischen Präparaten wurde modifiziert, um die Beständigkeit der Farbe, die Geschwindigkeit der Bestimmung und deren Empfindlichkeit zu verbessern. Statt in Wasser wird die Reaktion in Propan-2-ol durchgeführt, wobei Triethanolamin als Puffer und Jod — wenn nötig — als Oxydationsmittel verwendet werden. Die Farbe ist ungefähr 45 min beständig, die Empfindlichkeit der Reaktion stark verbessert und die zur Durchführung der Methode erforderliche Zeit beträgt etwa ein Fünftel im Vergleich zur USP-Methode.

     

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 tantalum in titanium alloys

Experimental work on tantalum-titanium alloys has been handicapped by the lack of accurate methods for the determination of the tantalum. In this paper a colorimetric procedure is proposed for the determination. The tantalum is separated completely from the titanium by two tannin precipitations with an intervening digestion with tannin. The tannin precipitate is ignited, fused with potassium bisulfate and the melt taken up with ammonium oxalate solution. Pyrogallol is then added and the intensity of the yellow color is measured. A study was made of the tantalum pyrogallol color to obtain optimum conditions. Elements that would be found in the usual tantalum-titanium alloys do not interfere with the method. More than 0.0025 gram of niobium interferes by cauaing occlusion of titanium by the tannin precipitate. This causes high results for tantalum, since titanium reacts with pyrogallol to produce a yellow color. The presence of more than 0.0050 gram of tungsten causes high results for tantalum because tungsten is partially precipitated by the tannin and reacts with pyrogallol to produce a yellow color. The proposed method is recommended for tantalum-titanium alloys containing 0.05 to 5 percent, tantalum.     

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.