Determination ofβ-Mercaptopyruvic acid in cysteine transamination mixture by titration with o-Hydroxymercuribenzoic acid using dithiofluorescein as an indicator

Summary A rapid and direct thiotitrimetric method for the determination of-mercaptopyruvic acid is described.o-Hydroxymercuribenzoic acid is used as a direct titrant with dithiofluorescein as an indicator. Cysteine and other thiol compounds which have a primary or secondary amino group can be inactivated by formaldehyde to form thiazolidine derivatives.-Mercaptopyruvic acid can be successfully determined to the limit of 0.2mol with an error less than 5% in the presence of-ketoglutarate, glutamate, PLP, as well as cysteine. The procedure described can be employed for the determination of-mercaptopyruvic acid formed during cysteine transamination using a rat liver extract as the enzyme source.

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Zusammenfassung Eine rasche Methode zur direkten thiomaßanalytischen Bestimmung von-Mercapto-Brenztraubensäure wurde beschrieben. o-Hydroxy-mercuribenzoesäure dient als Maßlösung mit Dithiofluorescein als Indikator. Cystein und andere Thiolverbindungen mit einer primären oder sekundären Aminogruppe können mit Formaldehyd zu Thiazolidinderivaten umgesetzt und damit inaktiviert werden.-Mercapto-Brenztraubensäure läßt sich bis zu 0,2Mol in Gegenwart von-Ketoglutarat, Glutamat, Pyridoxalphosphat und Cystein auf 5% genau bestimmen. Das Verfahren eignet sich zur Bestimmung von-Mercaptobrenztraubensäure, die bei der Transaminierung von Cystein mit Hilfe eines Rattenleberextraktes entsteht.

     

Radical polymerization as an indicator reaction for determination of organic compounds

Polymerization of methyl methacrylate (MMA) and 4-vinylpyridine (VP) has been carried out in an aqueous solution in the presence of the initiating system persulfate-tetramethylethylenediamine. The reaction rate has been monitored by measuring the light absorbance of the suspension of the resulting polymer. The effect of 26 model organic compounds on the polymerization rate has been studied. It has been shown that the VP polymerization is inhibited by a smaller number compounds (9 compounds) than the MMA polymerization (22 compounds), which indicates that the former reaction has better selectivity, whereas the determination of model compounds using the MMA polymerization reaction is more sensitive. This is explained by the lower chain growth rate constant for VP vs. MMA and different stationary concentrations of radicals in the systems. The use of these indicator polymerization reactions makes it possible to distinguish some closely related compounds, e.g., 1,4-benzoquinone and 9,10-anthraquinone (MMA reaction) or dinitrophenol and 4-nitrophenol or phenol (VP reaction). Determination of ascorbic acid in a pharmaceutical formulation has been carried out.     

Complexometric determination of thorium using p-nitrobenzene-azo-chromotropic acid (chromotrope 2-B) as indicator

Summary p-Nitrobenzene-azochromotropic acid (chromotrope 2 B) has been found useful as metal indicator in the titration of thorium ions against ethylenediaminetetraacetic acid. Titrations are best carried out with concentrations of thorium upto 0.001 M, within the p_H range 1.5 and 2.9. Temperature has no effect on the end point. Many of the common ions interfere in the titration excepting lithium, sodium, potassium, gold, alkaline earths, zinc, mercury, aluminium, lead, nickel, and acetate. Iron(III) if present may be masked by the addition of ascorbic acid.

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Zusammenfassung p-Nitrobenzol-azochromotropsäure (Chromotrope 2 B) wird als Metallindicator bei der komplexometrischen Titration von Thorium verwendet. Die besten Ergebnisse erhält man bei Konzentrationen bis 0,001 m im p_H-Bereich von 1,5–2,9. Die Temperatur hat keinen Einfluß auf die Erkennung des Endpunkts. Lithium, Natrium, Kalium, Gold, Erdalkalien, Zink, Quecksilber, Aluminium, Blei, Nickel und Acetat stören nicht, während viele andere Ionen Störungen verursachen. Eisen(III) kann mit Ascorbinsäure maskiert werden.

     

Titrimetric determination of organofluorine using Arsenazo I as indicator

Summary Some improvements of the titrimetrio method for determining fluorine in organic compounds are described. The modifications involve:(a) introduction of a combustion aid for the electrically heated flask combustion to insure complete conversion of fluorine to hydrogen fluoride, (b) employment of a glycine-perchlorate buffer to maintain a consistent stoichiometric titration, and (c) adaptation of an automatic titrimeter for photometric titration to simplify the detection of the end point. It is also suggested that a linear equation be derived from the calibration data in order to calculate the fluorine content.

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Zusammenfassung Einige Verbesserungen der maßanalytischen Bestimmungsmethode für Fluor in organischen Substanzen wurden beschrieben, nämlich: a) Einführung eines Zusatzreagens zur Erzielung einer vollständigen Überführung in Fluorwasserstoff bei der elektrischen Verbrennung im verschlossenen Kolben; b) Verwendung einer Pufferlösung von Glycin und Perchlorat zur Gewährleistung einer stöchiometrischen Titration; c) Anpassung eines automatischen Titriergerätes für photometrische Titrationen zwecks besserer Wahrnehmung des Endpunktes. Außerdem wird empfohlen, zur Berechnung des Fluorgehaltes eine lineare Gleichung zu verwenden.

     

Chromatographic determination of phthalic acid esters as an indicator of adulterated cognacs and cognac spirits

Based on the study performed, a conclusion was drawn that a system of procedures should be introduced into the practice of arbitration laboratories in order to identify the authenticity of cognacs and cognac spirits. These procedures were exemplified in the identification of diethyl phthalate in cognacs. Factors responsible for the falsely positive detection of diethyl phthalate in cognacs and cognac spirits were revealed. A substance that has a retention time equal to that of diethyl phthalate was identified as monoethyl succinate. As an example, recommendations were given for revealing adulterated cognac samples upon the detection of phthalic acid esters in them (including diethyl phthalate, which is a marker of denaturation). Sources of the contamination of test samples with diethyl phthalate were identified; an algorithm was developed for distinguishing between diethyl phthalate as an impurity component and diethyl phthalate added to an alcohol as a denaturation marker.     

Colorimetric and visual determination of DNase I activity using gold nanoparticles as an indicator

Patients with prostate cancer and systemic lupus erythematosus exhibit reduced DNase I activity, and patients with myocardial infarction exhibit increased DNase I activity. So the assay of DNase I is of high importance. A colorimetric assay is described here for the determination of the activity of DNase. It is based on strand scission of dsDNA as catalyzed by DNase I. The products of digestion (nucleoside monophosphates) can better stabilize citrate capped AuNPs than dsDNA. In the absence of DNase I, the AuNPs aggregate in presence of NaCl and then display a blue color. In the presence of the analyte (DNase I), AuNPs do not aggregate but rather remain dispersed and display a red color. These findings were exploited to design a DNase I activity assay that is based on the measurement of ratio of absorbances at 520 nm (red) to 650 nm (blue). The detection limit for DNase I activity is found to be 7.1 U?L^?1. In our perception, this assay has a large potential with respect to diagnoses of DNase I activity-related diseases and in drug screening.

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Graphical Abstract A method is described for the determination of the activity of DNase I. It is based on the capability of nucleoside monophosphates (dNMPs; formed by DNase-catalyzed scission of dsDNA) to stabilize red gold NPs against NaCl-induced aggregation. AuNPs stabilized with dsDNA, in contrast, readily aggregate in presence of NaCl to form blue clusters.

     

The determination of benzene in human blood as an indicator of environmental exposure to volatile aromatic compounds

Summary For the determination of ecologically caused benzene levels in human blood samples and for the evaluation of reference values for the general population a sensitive and reliable method was developed. The determination is performed by dynamic head space chromatography and FID-detection. The detection limit is 80 ng/l blood. The main problem is the avoidance of contamination during the preanalytical phase; precautions and recommendations are given. The mean benzene levels of nonsmokers are 176±62 ng/l, of smokers 211±85 ng/l; active smokers showed levels of 365±178 ng/l.     

Ferrimetric determination of uranium using rhodamine 6G as fluorescent indicator

Experimental conditions have been developed for the titration of uranium^IV with iron^III alum solution, using Rhodamine 6G as a fluorescent indicator. The titration is best carried out at 98–100° in a 2–3N hydrochloric acid medium, under filtered ultraviolet light, using 2.0 ml of 0.05% Rhodamine 6G solution for 30 ml of the titration mixture. A slight excess of iron^III solution quenches the greenish-yellow fluorescence of the dye through inner filter action. With the titration assembly described here, it is possible to determine uranium^IV with an accuracy of about 0.4%. This method appears to be more convenient than the potentiometric titration or the method employing potassium thiocyanate as internal indicator.

Evidence is also presented to show that the reaction between uranium^IV and iron^III is slow at room temperature.     

Mercurimetric determination of chloride with diphenylcarbazide disodium disulfonate as an indicator

A procedure is given for the use of diphenylcarbazide disodium disulfonate as an indicator in the direct titration of chloride with mercuric nitrate. By adding ferric nitrate to form the carbazone and an inert green substance to serve as a color screen, a sharp and reversible endpoint changing from green to grey to purple is obtained. Studies were made on the indicator reaction and other factors, such as mercuric chloride concentration, pH, volume, temperature and the effect of various added salts. The pH must be adjusted to 1.8 to 2.0 for best results. A series of ten determinations on a sample gave a standard deviation of ±0.16 part per thousand.     

Methyl violet as an indicator of perfluorosulfonic membrane acid properties

Sorption of methyl violet from an aqueous solution by a perfluorosulfonic membrane is accompanied by the indicator protonation. Changes in the absorption spectra of the indicator and the corresponding color transitions, which are consistent with the shape of the isotherm of water adsorption by the membrane, characterize it as a strong solid acid.     

Complexometric determination of mercury(II) using Congo Red as indicator

Congo Red is suggested as an indicator for the direct titration of mercury(II) ions with EDTA or with potassium thiocyanate. An interference study of a number of cations has been made. The titration with thiocyanate is more advantageous than that with EDTA.     

Analytical applications of o-hydroxymercuribenzoic acid, dithiofluorescein and mercurated fluorescein

The application of the reagents mentioned in the title to titrimetric, photometric and fluorimetric analysis of several compounds of sulphur, nitrogen and mercury, including procedures for selective determinations, detection, location, identification and estimation in trace quantities, is reviewed.     

The titrimetric micro determination of sulphate using lead nitrate as titrant and dithizone as indicator

Summary The previously reported titrimetric determination of sulphate, using lead nitrate as titrant and dithizone as indicator has been developed for application to the micro scale. Attention has been directed in the titration procedure to the effect of foreign ions and their removal where necessary, the optimum conditions for the highest accuracy, and the precision attainable for the range 0.5 to 5 mg of sulphate (0.16 to 1.6 mg of sulphur). This procedure forms a highly satisf actor y basis for the micro determination of sulphur in organic compounds by oxidation with nitric acid in a sealed tube and subsequent titration of the sulphate ion produced.The procedure has also been extended to the submicro scale giving a direct titration of 10 to 100g of sulphate (4–30g of sulphur), thus enabling the sulphur content of submicro quantities of organic compounds to be readily determined.

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Zusammenfassung Die kürzlich veröffentlichte Methode der maßanalytischen Schwefelbestimmung mit Bleinitrat unter Verwendung von Dithizon als Indikator wurde dem Mikromaßstab angepaßt. Auf die Störung durch Fremdionen und deren gegebenenfalls notwendige Entfernung wurde Bedacht genommen, die optimalen Bedingungen für größte Genauigkeit für den Bereich von 0,5 bis 5 mg Sulfat (0,16 bis 1,6 mg Schwefel) ermittelt. Das Verfahren bietet einen sehr befriedigenden Weg für die Mikrobestimmung des Schwefels in organischen Substanzen durch deren Oxydation mit Salpetersäure im geschlossenen Rohr und nachfolgende Titration des Sulfats.

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Rèsumè La méthode précédemment décrite pour le dosage titrimétrique des sulfates à l'aide de nitrate de plomb comme réactif titrant et de dithizone comme indicateur a été étendue au domaine microanalytique. La technique de titrage a été particulièrement étudiée des points de vue de l'effet des ions étrangers et de l'éventuelle nécessité de leur élimination, des conditions optimum pour atteindre l'exactitude la plus élevée et pour déterminer la précision qu'il était possible d'obtenir pour le domaine de 0,5 à 5,0 mg de sulfate (0,16 à 1,6 mg de soufre). Cette technique est extrêmement satisfaisante pour son application au microdosage du soufre dans les composés organiques après oxydation par l'acide nitrique en tube scellé et titrage ultérieur de l'ion sulfurique formé.

     

Volumetric determination of primary arylamines and nitrites, using an internal indicator system

A new nitrite titration method is presented. The titration is performed in the presence of a standard solution of 4,4'-sulphonyl-dianiline and diphenylamine, which is used as an internal indicator. An intense red colour develops during the titration as a result of a simultaneous diazotization and coupling process. A very sharp end-point is given by a colour change to yellow. The titration is performed at a temperature of about 45 degrees in the presence of large amounts of nitrate. The method is specific and precise. It is suitable for the direct volumetric determination of various easily diazotized primary arylamines, sulphonamides and other amino-compounds which can be determined by nitrite titration. It is suitable also for the indirect determination of nitrites. The method is applicable on the semimicro and macro scales.     

Microdetermination of thiocyanates with N-Bromosuccinimide using bordeaux red as an indicator

Summary N-bromosuccinimide has been used as a direct titrant for thiocyanates. Bordeaux red has been used as an indicator. In case of ammonium thiocyanate, nitrogen is evolved. While in case of potassium thiocyanate 0.5- to 2-mg samples were analyzed and maximum relative standard deviation was 1% in case of 0.5-mg sample. In case of ammonium thiocyanate 0.3- to 2.5-mg samples were analyzed and maximum relative standard diviation was 0.9% in case of 0.7-mg sample. The method is quick, precise and accurate.

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Zusammenfassung N-Bromsuccinimid wurde als Maßlösung zur direkten Titration von Thiocyanat verwendet. Bordeauxrot diente hierbei als Indikator. Bei der Titration von Kaliumrhodanid betrug die relative Standardabweichung 2% (bei 0,5 mg Einwaage), im Falle von Ammoniumrhodanid 0,9% (bei 0,7 mg Einwaage).

     

Colchiceine as an extractive indicator in the determination of copper(II)

Colchiceine, a new extractive indicator, is satisfactorily used in the determination of copper(II). A highly sensitive greenish yellow complex is formed with copper, which is extractable into chloroform. The results are comparable in sensitivity and selectivity with those of its precursors.