A new sensitive and specific test for cobalt

Summary The p-nitrophenylhydrazone of 3-isonitrosopentane-2-one gives in ammoniacal solution a red coloration with cobalt, which provides a sensitive and specific test. Cyanide as well as a high concentration of ammonium salts prevent the test. Palladium, silver, nickel, copper and most common cations and anions do not interfere.

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Zusammenfassung Dasp-Nitrophenylhydrazon von 3-Isonitrosopentan-2-on gibt in ammoniakalischer Lösung mit Kobalt eine Rotfärbung, die dessen empfindlichen und spezifischen Nachweis ermöglicht. Cyanid sowohl wie eine hohe Ammoniumsalzkonzentration verhindern die Probe. Palladium, Silber, Nickel, Kupfer und die meisten der gewöhnlichen Kationen und Anionen verursachen keine Störung.

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Résumé Lap-nitrophenylhydrazone de l'isonitroso-3 pentanone-2 donne en solution ammoniacale une coloration rouge avec le cobalt que l'on utilise comme essai sensible et spécifique. Les cyanures, ainsi que de fortes concentrations en sels de l'ammonium, gênent l'essai. Le palladium, l'argent, le nickel, le cuivre et les cations et anions les plus fréquents n'interfèrent pas.

     

A new sensitive and specific test for vanadium with sulphosalicylic acid

A very sensitive and specific test for vanadium^V is described using sulphosalicylic acid as reagent. When this reagent is brought into contact with solid vanadium^V (a drop of the test solution evaporated to dryness on a watch glass) in the presence of concentrated sulphuric acid or 80% syrupy phosphoric acid, a blue colour is developed. Using this colour reaction, it is possible to detect 0.05 μg of vanadium^V in 0.05 ml of test solution. Aluminium^III, arsenic^V, beryllium^II, cadmium^II, chromium^III, chromium^VI, copper^II, iron^III, molybdenum^VI, nickel^VI, tungsten^VI, uranium^VI and vanadium^IV do not interfere with this colour test, although some of them are known to form coloured complexes with sulphosalicylic acid under different conditions. Reducing agents like iron^II, uranium^IV, molybdenum^V and hydroquinone discharge the colour. The colour of the vanadium^V-sulphosalicylic acid compound is also discharged if the temperature is raised to 60°, though it reappears on cooling.     

On the reactivity of innercomplex-bonded palladium : A new specific test for cyanides in alkaline solutions

It has been found that the innercomplex salts of palladium with dimethylglyoxime, (benzildioxime and furildioxime), salicylaldoxime and 8-hydroxyquinolinc do not enter into redox reaction with carbon monoxide, cither in solid or in molecular dispersed form.Solutions of palladium-dimethylglyoxime and palladium-salicylaldoxime in alkali hydroxide or ammonia are masked with respect to many reactions of the palladium as well as of the organic components. In alkaline solutions, when adding alkali cyanide, demasking occurs, with the deliberation of the innercomplex forming organic components. For the processes of dissolution and demasking appropriated equations are suggested.The demasking of dimethylglyoximc in alkaline solutions of palladium dimethylglyoxime permits a new sensitive test for cyanide ion. This cyanide test seems to be appropriate for the detection of illuminating gas.Palladium hydroxyquinorate is insoluble in solutions of alkali cyanides, though it is not precipitable from cyanide containing palladium solutions. An explanation for this “false equilibrium” is suggested.     

A new spot test for fluoride

Summary Solution of silver ion, which is stable in the presence of appropriate concentrations of ferrous and ferric salts, is reduced by ferrous salts if fluoride is added. This fact has been utilized to develop a spot test for fluoride. 2g of fluoride ion can be detected. A method for the removal of fluoride from interfering ions is also described.

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Zusammenfassung Silberlösungen, die in bestimmten Konzentrationen von Eisen(II)- und Eisen(III)-salzen beständig sind, werden von Eisen(II)-salzen reduziert, wenn man Fluorid zusetzt. Auf dieser Grundlage wurde eine Tüpfelreaktion für Fluorid ausgearbeitet. 2 g F^– können damit nachgewiesen werden. Eine Methode zur Abtrennung von Fluorid von störenden Ionen wurde ebenfalls angegeben.

     

A new spot test for silver

Summary A new spot test for silver has been developed. Test papers are prepared by impregnating filter paper with an equilibrium mixture of potassium tetracyanonickelate and dimethylglyoxime. As little as 0.5g of silver can be detected.

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Zusammenfassung Ein neuer Tüpfelnachweis für Silber wurde ausgearbeitet. Man imprägniert Filtrierpapier mit einer Gleichgewichtslösung von Kaliumnickeltetracyanid und Dimethylglyoxim. 0,5g Silber können nachgewiesen werden.

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Résumé On a mis au point un nouvel essai à la touche de l'argent. Les papiers servant aux essais sont préparés par imprégnation de papier filtre par le mélange de tétracyanonickelate de potassium et de diméthylglyoxime ayant la composition d'équilibre. On peut ainsi détecter des traces d'argent de 0,5g.

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On leave from The College of Engineering and Technology, Bengal Jadavpur, Calcutta-32, India     

A new spot test for oximes

Summary Oximes couple in alkaline medium with diazonium salts to give arylazo-bis-oximes which develop an intense blue colour with ferric chloride; 50g of an oxime can be detected in 0.25 ml of total solution on a spot-plate by this method.

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Zusammenfassung Oxime Kuppeln in alkalischem Medium mit Diazoniumsalzen unter Bildung von Arylazo-bis-oximen, die ihrerseits mit Eisen(III)-chlorid eine intensive Blaufärbung geben. 50g Oxim können so in 0,25 ml Reaktionsgemisch auf der Tüpfelplatte nachgewiesen werden.

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The authors express their gratitude to ProfessorR. C. Mehrotra for providing facilities in the Department.     

A new test for 'sufficient homogeneity'

Certified reference materials and materials distributed in proficiency testing need to be 'sufficiently homogeneous', that is, the variance in the mean composition of the distributed portions of the material must be negligibly small in relation to the variance of the analytical result produced when the material is in normal use. The requirement for sufficient homogeneity suggests the use of a formal test. Such tests as have been formulated rely on the duplicated analysis of the material from a number of portions, followed by analysis of variance. However, the outcome is not straightforward. If the analytical method used is very precise, then an undue proportion of the materials will be found to be significantly heterogeneous. If it is too imprecise, the test may be unable to detect heterogeneity. Moreover, the Harmonised Protocol Procedure (M. Thompson and R. Wood, Pure Appl. Chem., 1993, 65, 2123) seems to be unduly prone to the rejection of material that is in fact satisfactory. We present a simple new statistical approach that overcomes some of these problems.     

A new spot test for palladium

A new Spot test foi palladium is based upon the formation of an orange-yellow chelate with phenyl-α-pyridyl ketoxime Interference by the metals usually associated with palladium can be easily and completely prevented. Lumit of identification 0 5μg Pd     

A simple specific test for inner-ring o-quinones

A simple specific test for inner-ring o-quinones is introduced. The test consists of the reaction of the quinone with 3,4-dimethoxyamline in hot acetic acid to give dye(s) absorbing near 600 mμ Spot test and colorimetric rnoditications of the test are described Other types of quinones and ketonic compounds give negative results The spectra of the o-quinones in sulfuric acid are also presentedWith the new method, fairly specific tests are now available for (a) inner-ring p-quinones, (b) inner-ring o-quinones, and (c) terminal ring o- and p-quinones     

A new specific fullerene-based fluorescent probe for trypsin

A novel fluorescent probe (C(60)-FL) was designed and synthesized for the direct determination of trypsin, based on photo-induced electron transfer (PET). The probe consists of two functional moieties: fluorescein which performs as a fluorophore and an electron donor, and fullerene (C(60)) which acts as an electron acceptor and trypsin substrate analogue. In the presence of trypsin, the probe exhibited fluorescence increase due to the inhibition of electron transfer by the combination of C(60)-FL with trypsin. The response of the probe to trypsin was direct and rapid. Experimental results showed that the increase in fluorescence intensity is proportional to the concentration of trypsin within the range of 4.40×10(-7) to 7.04×10(-5) g mL(-1) under the optimized experimental conditions. The detection limit of the proposed method was 40 ng mL(-1). The method had high selectivity for trypsin over other enzymes and proteins, such as lipase, α-amylase, bovine serum albumin, zinc metallothionein, glutathione reductase, thioredoxin and α-chymotrypsin etc. The remarkable properties of C(60)-FL help to extend the development of fluorescent probes for investigating enzymes in a biological context.     

A new spot test for carboxylic acids

Summary A method for the detection ofg amounts of carboxylic acids, based on the conversion of carboxylic acids to hydroxamic acids using ethylene glycol or dicyclohexylcarbodiimide and subsequent detection as reddish-violet vanadium(V) complex, is presented. The method tolerates the presence of anions and cations including SO₄ ^2–, Br^–-, PC₄ ^3–, Mg(II), Ca(II), Na(I), Fe(II), Fe(III), Cu(II). The test for benzoic acid was independent of the presence of benzene, aniline, diethyl ether, benzenesulfonic acid and phenol. Aryl chlorides, esters, amides and anhydrides interfere with the test.

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Zusammenfassung Der Nachweis von Mikrogrammengen Carbonsäure läßt sich auf der Grundlage der Überführung in Hydroxamsäure und nachherige Bildung der rötlich-violetten Komplexverbindung mit Vanadin(V) durchführen. Dabei stören folgende Ionen nicht: SO₄ ^2–, Br^–, PO₄ ^3–, Mg(II), Ca(II), Na(I), Fe(II), Fe(III), Cu(II). Der Nachweis der Benzoesäure ist unabhängig von der gleichzeitigen Anwesenheit von Benzol, Anilin, Diäthyläther, Benzolsulfonsäure und Phenol. Arylchloride, Ester, Amide und Anhydride stören die Reaktion.

     

A new test for the mercurous ion

Summary The enhancement of the reducing power of the mercurous ion in presence of thiocyanate can be used for its detection. The most suitable method is to add an excess of thiocyanate and ferric salt, and to detect the ferrous ion formed with o-phenanthroline or dimethylglyoxime. With the former the sensitivity (pD) is 5.0 and the interferences are Cu²⁺, PtCl ₆ ^2- , Co²⁺, Fe²⁺ and Sn²⁺. With the latter the sensitivity (pD) is 4.7, and the interferences are Cu²⁺, Co²⁺, Ni²⁺, Fe²⁺, Sn²⁺, PtCl ₆ ^2- and VO ₃ ^- .Similar reactions can be used for the detection of metallic mercury but many metals interfere.Some other redox indicator system can also be used, but they are less applicable than the system indicated above.

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Zusammenfassung Die bei Gegenwart von Rhodanid erhöhte reduzierende Wirkung von Quecksilber-I-Ionen kann zu deren Nachweis verwendet werden. Am besten fügt man einen Überschuß von Rhodanid und Eisen-III-Salz zu und weist die gebildeten Eisen-II-Ionen mit o-Phenanthrolin oder Dimethyldioxim nach. Bei Anwendung des ersteren Reagens beträgt die EmpfindlichkeitpD = 5,0, wobei Cu⁺⁺, PtCl ₆ ^-- , Co⁺⁺, Fe⁺⁺ und Sn⁺⁺ stören. Bei Anwendung von Dimethyldioxim beträgt die EmpfindlichkeitpD = 4,7, wobei Cu⁺⁺, Co⁺⁺, Ni⁺⁺, Fe⁺⁺, Sn⁺⁺, PtCl ₆ ^-- und VO ₃ ^- stören.Ähnliche Reaktionen können zum Nachweis von metallischem Quecksilber dienen, werden aber von vielen Metallen gestört.Einige andere Redox-Indikator-Systeme können gleichfalls herangezogen werden, sind aber weniger gut anwendbar.

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Résumé On peut utiliser l'exaltation du pouvoir réducteur de l'ion mercureux en présence de thiocyanate pour sa détection. La méthode la plus convenable consiste à ajouter un excès de thiocyanate et de sel ferrique et de détecter l'ion ferreux formé avec l'o-phénanthroline ou la diméthylglyoxime. Avec la première, la limite de sensibilité estpD = 5,0 et les interférences sont dues à Cu²⁺, PtCl ₆ ^2- , Co²⁺, Fe²⁺ et Sn²⁺. Avec la dernière, la sensibilité estpD = 4,7 et les interférences sont dues à Cu²⁺, Co²⁺, Ni²⁺, Fe²⁺, Sn²⁺, PtCl ₆ ^2- et VO ₃ ^- .Des réactions similaires peuvent être employées pour la recherche du mercure métallique mais de nombreux métaux interfèrent. D'autres systèmes redox peuvent être aussi utilisés mais ils se montrent moins convenables que les précédents.

     

A new spot test for nitro compounds

A simple, rapid, and highly sensitive method for the detection of micro amounts of nitro compounds has been developed. Nitro compounds are reduced into corresponding hydroxylamines with zinc dust and acetic acid and coupled with diazonium chloride to give hydroxytriazines which give an intense pink to violet color with diphenylamine in acetic acid medium. Quantities of 0.1 μg or less of nitro compounds can be detected in 0.25 ml of total solution by this method. The method is free from the common interference.     

A new role for old ligands: discerning chelators for zinc metalloproteinases

In an effort to identify promising non-hydroxamate inhibitors of matrix metalloproteinases (MMPs) several new zinc-binding groups (ZBGs) based on pyridine-derived or aza-macrocycle chelators have been examined. Fluorescence-based enzyme assays have been used to determine the IC50 values for these ZBGs against MMP-1, MMP-3, and anthrax lethal factor (LF). Many of these ligands were found to be remarkably potent, with IC50 values as much as 185-fold lower than that found for acetohydroxamic acid. These ligands are proposed to be more selective "warheads" for the inhibition of metalloenzymes that contain Zn2+ versus other metal ions at their active site.