Spectrophotometric estimation of reducing sugars by variation of pH

Summary A Spectrophotometric method of estimation of glucose and maltose using 3,5-dinitrosalicylic acid and measuring the color intensity at two different pH values is described. The concentrations of sugars in unknown solutions are calculated from a linear plot which is obtained when the difference in absorbances at 560 nm for solutions with pH 12.5 and 5.0 (A=A _pH12.5–A_pH5.0) is drawn against concentrations of sugars (up to 3 mg/ 25 ml). This method eliminates the interference caused by the unreacted reagent present in the conventional method. The present method can be used for the estimation of glucose and maltose upto a concentration of 1.5 mg/ml with an error of ±2.0%.

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Spektralphotometrische Bestimmung reduzierender Zucker durch Veränderung des pH-Wertes

Zusammenfassung Die Bestimmung von Glucose und Maltose wird mit 3,5-Dinitrosalicylsäure durch Messung bei zwei verschiedenen pH-Werten durchgeführt. Eine lineare Eichkurve wird bis 3 mg/25 ml erhalten, wenn man die Extinktionsdifferenz für pH 12,5 und 5,0 bei 560 nm gegen die Konzentration aufträgt. Durch dieses Verfahren wird die bei der konventionellen Methode auftretende Störung durch nicht umgesetztes Reagens ausgeschaltet. Bis zu 1,5 mg/ml der Zucker können mit einem Fehler von ±2% bestimmt werden.

     

The microdetermination of reducing sugars in blood by means ofp-Anisyl tetrazolium blue

Summary Glucose reacts mole per mole with a solution of 1 mg/ml ofp-Anisyl tetrazolium blue at p_H 12.5 and boiling for 45 to 60 seconds to give the insoluble blue diformazan. A minimum of 1g and a maximum of 200g of glucose may be estimated with a relative standard deviation of±0.03. These values are equivalent to a reducing sugar concentration from 4 to 800 mg per 100 ml of blood if the procedure is followed as outlined. One microgram of glucose changes the absorbance by 0.018; the corresponding figures for the method ofNelson andSomogyi and the procedure ofSaifer, Valenstein andHughes ²¹ are 0.006 and 0.009, respectively.Since the blood filtrates are deproteinized by the Somogyi procedures using zinc hydroxide, reducing substances like glutathione and glucuronic acid are removed, and the results approach a true blood sugar. The normal values for blood sugar obtained by the proposed method are practically the same as those given by the clinically accepted NelsonSomogyi procedure, i. e. 85±20 mg/ml. The root mean square of the differences in the results of the two methods is±4 mg glucose per 100 ml blood.

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Zusammenfassung Ein Mol Glukose reagiert mit einem Molp-Anisyltetrazoliumblau (I) unter Bildung des unlöslichen blauen Diformazans, wenn man Lösungen von 1 mg I/ml bei ph=12,5 anwendet und nicht länger als 45 bis 60 Sekunden gekocht wird. Glukosemengen von l bis 200g können mit einem relativen mittleren Fehler von ±0,03 bestimmt werden. Diese Mengen entsprechen Blutzuckerkonzentrationen von 4 bis 800 mg%, wenn das beschriebene Verfahren angewendet wird.Die optische Dichte ändert sich um 0,018 Einheiten jeg Glukose; die entsprechenden Zahlen für die Verfahren vonNelson undSomogyi bzw. vonSaifer, Valenstein undHughes ²¹ sind 0,006 und 0,009.Da das Blut ebenso wie vonSomogyi unter Benutzung von Zinkhydroxyd enteiweißt wird, wodurch reduzierende Substanzen, wie Glutathion und Glukuronsäure, entfernt werden, ist anzunehmen, daß die Resultate den tatsächlichen Blutzuckergehalten nahekommen. Der normale Blutzuckergehalt wird ganz ähnlich wie mit der in klinischen Laboratorien üblichen Methode vonNelson undSomogyi zu 85±20 mg% gefunden. Die Wurzel aus dem Mittel der Quadrate der Differenzen der Resultate der beiden Methoden beträgt ±4 mg%.

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Résumé Le glucose réagit, molécule pour molécule, avec une solution de bleu dep-anisyltétrazolium à p_H 12. 5 après ébullition pendant 45 à 60 secondes, pour donner un précipité bleu de diformazane.On peut ainsi estimer un minimum de 1g et un maximum de 200g de glucose avec un écart type relatif de ±0,03. Ces valeurs sont équivalentes à une concentration de sucre réducteur variant de 4 à 800 mg par 100 ml de sang si la technique est appliquée commeil est indiqué. Un microgramme de glucose fait varier l'extinction de 0,018 tandis que les valeurs correspondantes sont respectivement de 0,006 et 0,009 dans la méthode deNelson-Somogyi et la technique deSaifer, Valenstein etHughes.Les filtrats de sang étant déprotéinés d'après la technique deSomogyi à l'hydroxyde de zinc, les substances réductrices telles que le glutathion et l'acide glucuronique sont éliminées de sorte que les résultats sont voisins de la teneur réelle en sucre du sang. Les valeurs normales du sucre sanguin obtenues par la méthode proposée sont pratiquement les mêmes que celles fournies par la méthode deNelson-Somogyi employée en clinique, c'est-à-dire 85 ±20 mg/100 ml. La racine carrée du carré moyen des écarts des résultats des deux méthodes est de ±4 mg de glucose par 100 ml de sang.

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Dedicated to ProfessorHans Lieb on occasion of his 70th birthday.     

Chemiluminescent reaction of lucigenin with reducing sugars

The chemiluminescent reaction, in alkaline solution, of lucigenin with the reducing sugars sorbose, fructose, lactose, glucose, xylose, galactose, arabinose and mannose has been studied. There is a linear relationship (correlation coefficient = 0.996) between the emission intensity and the second-order rate constant for the alkaline oxidation of these sugars. The emission intensity is linearly related to the sugar concentration; at high sugar concentrations (5mM) it is independent of the lucigenin concentration, but at low concentrations (<0.05mM) is linearly related to the lucigenin concentration. These facts support the view that the rate-limiting step is the tautomerization of the sugars to the 1,2-enediol form; the enediol then undergoes reaction with lucigenin.     

Titrimetric semimicro determination of reducing sugars in wines and liquors

Summary A semimicro modification of the method ofFehling-Causse-Bonnams is described for the determination of invert sugar in wines and liquors. A relative standard deviation of 4 parts per thousand is obtained by closely adhering to a standardized procedure which is also required for the attainment of accuracy.

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Zusammenfassung Ein Halbmikroverfahren der Methode vonFehling-Causse-Bonnams wird für die Bestimmung von Invertzucker in Wein und Likören beschrieben. Der relative mittlere Fehler konnte durch Konstanthaltung der Versuchsbedingungen auf 0,4% beschränkt werden, eine Maßregel, die für die Erzielung richtiger Ergebnisse erforderlich ist. Die zur Entfärbung verwendete Pflanzenkohle adsorbiert auch etwa 2% des reduzierenden Zuckers pro 50 mg Kohle und der dadurch bedingte Korrektionsfaktor muß durch Kontrollanalysen mit Invertzuckerlösungen bekannten Gehaltes für jede Kohlesorte bestimmt werden.

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Résumé On décrit un procédé semi-micro pour la méthode deFehling-Causse-Bonnams pour le dosage du sucre interverti dans le vin et les liqueurs. L'erreur relative moyenne a pu être limitée à 0,4% par maintien constant des conditions de l'expérience; cette mesure est nécessaire pour l'obtention de résultats corrects. Le charbon végétal utilisé pour décolorer adsorbe environ 2% de sucre réducteur pour 50 mg de charbon et le facteur de correction qui en résulte doit, dans les analyses de contrôle, être déterminé pour chaque qualité de charbon avec des solutions de sucre interverti de teneur connue.

     

SPME-GC-MS检测尿液中甲卡西酮类毒品

建立了尿液中甲卡西酮类毒品顶空固相微萃取-气相色谱-质谱联用的含量测定方法。在添加定量甲卡西酮类标准品的尿液试样中,加入固体Na2CO3,以MDMA为内标,调溶液p H10,80℃下加热搅拌,用70μm乙烯二醇-二乙烯基苯共聚物(CW/DVB)萃取头顶空萃取20 min,GC-MS检测,获得良好线性,其标准曲线线性范围在0.06μg~1.86μg·m L-1,最小检测限可达0.01μg·m L-1,平均回收率均在85%~115%之间。相对标准偏差均在11%以内。     

Kinetics and mechanism of the oxidation of reducing sugars by osmium tetroxide in alkaline medium

A general mechanism for oxidizing reducing sugars (pentoses, hexoses and disaccharides) by OsO₄ in alkaline medium is proposed. The reactions exhibit pseudounimolecular kinetics with respect to OsO₄, are first order with respect to lower [sugar] and [OH⁻], but tend towards zeroth order with respect to both higher [sugar] and [OH⁻]. These results suggest the formation of an activated complex between the enediol andd osmium tetroxide, which slowly disproportionates to give osmium(VI) species and the intermediate products. The reaction products were identified. When an aldehydo sugar is treated with alkali, structural changes occur and an equilibrium is set up, mainly involving a keto sugar product and the starting aldehydo sugar consumed. This process is reversible. These changes are mainly due to the well-known Lobry-de-Bruyn-Alberda Van Ekenstein transformations. This revised version was published online in June 2006 with corrections to the Cover Date.     

Spectrophotometric determination of reducing sugars with aromatic nitro compounds

Summary It has been found that mononitro-aromatic compounds can be used as quite sensitive reagents for determination of reducing sugars, and use of 2-, 3- and 4-nitrobenzoic and 3-nitrobenzenesulphonic acids has been investigated. Reduction of these reagents with sugars gives a yellow product which can be determined spectrophotometrically. The sugar (0.5–7 mg) is heated with fixed concentrations of reagent, base and sodium potassium tartrate for a prescribed time, at 100° C. The method can also be used for determination of the number-average molecular weight of dextran fractions if the molecular weight is not too high.

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Spektrophotometrische Bestimmung reduzierender Zucker mit aromatischen Nitroverbindungen

Zusammenfassung Aromatische Mononitroverbindungen lassen sich als ziemlich empfindliche Reagenzien zur Bestimmung reduzierender Zucker verwenden. 2-, 3-und 4-Nitrobenzoesäure und 3-Nitrobenzolsulfonsäure wurden zu diesem Zweck verwendet. Die Reduktion dieser Reagenzien durch Zucker gibt eine Gelbfärbung, die spektrophotometrisch ausgewertet werden kann. Der Zucker (0,5-7 mg) wird mit einer bestimmten Menge Reagens sowie mit einer Base und Seignettesalz für eine bestimmte Zeit auf 100° C erhitzt. Das Verfahren kann auch für die Bestimmung des durchschnittlichen Molekulargewichtes von Dextranfraktionen verwendet werden, soferne diese nicht zu hochmolekular sind.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Streamlined synthesis of per-O-acetylated sugars, glycosyl iodides, or thioglycosides from unprotected reducing sugars

Solvent-free per-O-acetylation of sugars with stoichiometric acetic anhydride and catalytic iodine proceeds in high yield (90-99%) to give exclusively pyranose products as anomeric mixtures. Without workup, subsequent anomeric substitution employing iodine in the presence of hexamethyldisilane (i.e., TMS-I generated in situ) gives the corresponding glycosyl iodides in 75-95% isolated yield. Alternatively, and without workup, further treatment with dimethyl disulfide or thiol (ethanethiol or thiocresol) gives anomerically pure thioglycosides in more than 75% overall yield.     

Kinetics and mechanism of oxidation of some simple reducing sugars by permanganate ion in alkaline medium

The kinetics of oxidation of glucose, galactose, fructose, maltose and sucrose by alkaline permanganate anion has been studied. The reactions studied spectrophotometrically over a wide range of experimental conditions show that the rate of the reactions is enhanced by increase in pH, ionic strength, and temperature as well as the reactant concentrations. The mechanism has been proposed to proceed via the formation of enediol intermediate complexes and the order of reactivities of the sugars is fructose > glucose ≈ galactose > maltose > sucrose. The activation parameters were evaluated and lend further support to the proposed mechanism.     

Determination of reducing sugars with 3:6-dinitrophthalic acid

Reducing sugars are determined in the concentration range 10 ˜ 100 μg/ml using 3:6-dinitrophthalic acid as a colour developing agent. Individual pentoses, hexoses, and disaccharides give the same calibration curves, respectively. Sucrose is also determined in the presence of glucose or fructose.     

Determination of reducing sugars with a 2,4-dinitrophenolate-selective membrane electrode

A 2,4-dinitrophenolate-selective liquid-membrane electrode based on tetrapentylammonium dinitrophenolate dissolved in 2-nitrotoluene is described. The electrode exhibits rapid and near- Nernstian response to the activity of 2,4-dinitrophenolate anions in the range 3×10^?5 ?1×10^?2 M. The response is unaffected by pH in the range 7.5–12.5. The electrode has been successfully applied to the kinetic potentiometric determination of fructose, glucose and galactose at 60°C and of fructose in the presence of glucose and galactose at 30°C. The electrode can be used for the potentiometric determination of glucose and fructose after completion of the reaction with excess of 2,4-dinitrophenolate ions and of sucrose after acid hydrolysis. Mixtures of glucose, fructose and sucrose in aqueous solutions or honey samples can be determined by the proposed procedures with an average error of about 2%.     

Sequential injection system for the spectrophotometric determination of reducing sugars in wines

A sequential injection system for the spectrophotometric determination of reducing sugars in wines is described. The methodology is based on the formation of a coloured complex produced by the reaction of copper (I) with 2,9-dimethyl-1,10-phenanthroline (neocuproine), after reduction of copper (II) to copper (I) by reducing sugars. In the present SI system, a dialysis unit was incorporated not only to allow the sample dilution, but also to minimise the interference of some coloured compounds. In this way, direct sample introduction into the system was possible, without any previous treatment of the wine samples. The proposed method can be applied to the determination of reducing sugars in two concentration ranges: from 2 to 25 g l(-1) (table wines) and from 20 to 140 g l(-1) (Port wines). To perform determinations in these two ranges, the manifold configuration remained the same; just a few operational parameters were changed in the controlling software. A sampling-rate of 14-18 samples per hour was obtained with good repeatability for ten consecutive injections of wine samples (relative standard deviations (RSD) <2.1%). The results obtained from 19 wine samples were comparable to those obtained by the reference method.