In Process Citation

Eight commercial samples of eosin have been analysed. Three problems were encountered in selecting material for use as a drug: the degree of hydration, the inorganic content and, above all, the composition of the xanthene moiety, which could contain up to 8 dyes.     

In Process Citation

Two chromatographic methods are proposed for separation, identification and determination of dibenzoazepines and benzodiazepines. A micro thin-layer method has been developed and transposed to give an HPLC system, which requires a slight modilfication of the solvent. Retention data are given, and two quantitative applications arc described.     

In Process Citation

Maleic, fumaric, tartaric, glutaric and adipic acids are titrated directly with sodium hydroxide by means of an automatic thermometric titrimeter. The titration curves have two break-points, corresponding to the successive neutralization of the two acid groups. Previous standardization permits measurement of the heats of neutralization, from which the enthalpies of dissociation can be deduced. From 0.3 to 1 mmole of acid can be titrated with a relative standard deviation of about 3%.     

In Process Citation

In the presence of an alkylamine, a guanidine or a quaternary ammonium hydroxide, liberated from their salts by the action of silver oxide, nitromethane reacts with 1,3,5-trinitrobenzene, yielding a red compound which allows the colorimetric determination of the nitrogenous base.     

In Process Citation

The chromatographic behaviour of zinc, cadmium and mercury on columns of natural cellulose and substituted celluloses is studied using (65)Zn, (109)Cd and (203)Hg radiotracers. Traces of zinc and cadmium are strongly retained by the functional groups attached on the substituted celluloses ; on the contrary mercury is not retained to any extent. Nanogram amounts of zinc, cadmium and other metals are separated from 3 g of mercury on cellulose phosphate in ethyl ether.     

In Process Citation

The reversibility of the determination reaction is the most frequent cause of deviations from linearity of thermometric titration curves. Because of this, determination of the equivalence point by the tangent method is associated with a systematic error. The authors propose a relationship which connects this error quantitatively with the equilibrium constant. The relation, verified experimentally, is deduced from a mathematical study of the thermograms and could probably be generalized to apply to other linear methods of determination.     

In Process Citation

The isotherms for adsorption of some organic molecules on asbestos fibres have been determined by gas chromatography. The results show that the adsorption mechanism lies somewhere between physisorption and chemisorption. The degree of adsorption at a given temperature, for the compounds studied, is toluene > tetrahydrofuran > benzene > dichlorométhane.     

In Process Citation

In the study of complex formation in aqueous solution by means of pH measurements, it is very useful to know the free ion concentrations in order to find each species composition and then calculate approximate values of their stability constants. From the pH determination alone, the unmeasured free ion concentrations can be calculated by a method in which a minimum number of integration and derivation steps are required. This process, called CILS, has been entirely computerized, and its conditions of application are illustrated with a simulated example.     

In Process Citation

After a statement of the main requirements for an analytical system to be suitable for use in industry, a detailed examination is made of the response of each part of an activation installation (choice of neutron source and detector, transfer system for standards and samples, data handling) to these requirements. Several applications already established in industry are mentioned (determination of oxygen, nitrogen, fluorine, silicon). Some continuous analyses are also mentioned.     

In Process Citation

Several flavonols of therapeutic interest on account of their vascular properties have been studied. They were all derived from the o-diphenol quercetol. Their electrochemical oxidation at a rotating solid electrode has been examined, and the choice of solvent and pH is discussed. Results obtained by d.c. and pulse polarography are presented. A relation between their structure and electrochemical behaviour has been established. Application to drug analysis is proposed, giving identification, determination and purity assay simultaneously. There is a linear response over the range 5 x 10(-6)-10(-4)M, a sufficient range for analysis of pharmaceuticals.     

In Process Citation

The absorption and fluorescence properties of six furoquinoline or pyranoquinoline alkaloids extracted from Rutaceae plants are described. These properties are related to the molecular structure and used for the fluorometric determination of two of them (platydesminium and balfourodinium) in Choisya ternata cell cultures and original plant extracts.     

In Process Citation

Knowing the values of the equilibrium constants corresponding to the reactions N(2)O(4) right harpoon over left harpoon 2NO(2) and N(2)O(4) right harpoon over left harpoon NO(+) + NO(3)(-) in sulpholane, we have undertaken the electrochemical study of N(2)O(4) by means of linear and cyclic voltammetry at the platinum electrode. The N(2)O(4) species undergoes one oxidation step N(2)O(4) right harpoon over left harpoon 2NO(2) right harpoon over left harpoon 2NO(2)(+) + 2e and two reduction steps NO(2) + N(2)O(4) + e(-)right harpoon over left harpoon N(2)O(3) + NO(3)(-) (1st wave), followed by 3N(2)O(4) + 2e(-) right harpoon over left harpoon 2N(2)O(3) + 2NO(3)(-), N(2)O(4) + e(-) right harpoon over left harpoon NO + NO(3)(-), 2N(2)O(3) + e(-) right harpoon over left harpoon 3NO + NO(3)(-) (2nd wave). The redox properties of N(2)O(4) are complicated by trace quantities of water because of the formation of the electroactive species N(2)O(3), HNO(3) and HNO(2) according to N(2)O(4) + H(2)O right harpoon over left harpoon HNO(2) + HNO(3) and N(2)O(4) + HNO(2) right harpoon over left harpoon N(2)O(3) + HNO(3). The standard potentials of the couples concerned have been evaluated and are discussed. sont discutés et évalués.     

In Process Citation

alpha-Amino acids are converted into fluorescent derivatives of dihydrolutidine. Primary and secondary alkylamines are determined by converting them into sulphonamides by means of 1-dimethylamino-naphthalene-5-sulphonyl chloride. A fluorescent adduct is given by the reaction of tertiary alkylamines with alpha,gamma-anhydroaconitic acid in acetic anhydride, and a fluorescence is obtained by condensing indoles with formaldehyde in the presence of an oxidizing agent. Furfural, obtained by the dehydration of pentoses, is determined by converting it into a 1,8-dioxodecahydroacridine derivative. 2,6-Di-t-butyl-p-cresol allows the fluorimetry of Delta(4) and Delta(1,4)-3,11-diketosteroids. The fluorescence of Pyronine G decreases under the action of Delta(5(10))-3-keto-19-norsteroids.     

In Process Citation

A method is proposed for determination of americium by coulometry. It is based on displacement of mercury(II) from its EDTA complex by americium and its subsequent electroreduction. The equivalence point is found by the "dead-stop" method. The cell and apparatus described will give a precision of about 0.1% for 700 mug of americium and 0.2% for 300 mug (relative standard error of the mean, 95% confidence) under optimum conditions. The measurement is absolute and prior standardization is not required. The determination takes about an hour. The results are compared with those obtained by other methods and interferences have been studied.     

In Process Citation

The electrochemical behaviour of some pyrazolone derivatives has been studied in aqueous and ethanolic media. beta-Diketone compounds with a labile hydrogen atom on carbon atom 4 are directly reducible in neutral ethanol; phenazone derivatives have to be diazotized. Pulse polarography is suggested for determination of these derivatives in pharmaceutical preparations.     

In Process Citation

The variation in heat capacity and the thermal shifts which accompany a thermometric determination make the thermogram, even in the case of a very rapid and irreversible reaction, hyperbolic instead of formed of straight segments. These departures from linearity, which are inconvenient in the interpretation and exploitation of the thermograms, can be calculated as a function of the degree of titration. The relation obtained introduces a parameter which the authors call the apparent change of capacity at the equivalence point, and which takes into account the two causes of deviation from linearity. This relationship is confirmed experimentally.     

In Process Citation

A method for the quantitative determination of cationic and non-ionic surfactants which is based on their inhibiting effect on certain electrochemical reactions has been developed. This technique enables one to determine, with a precision of 2–3%, these substances at concentrations of the order of 10⁻⁶M.

Zusammenfassung

Wir haben eine Methode eingestelt, um oberflächenaktiven kationischen und nicht ionischen Substanzen zu dosieren. Diese Methode ist auf ihren Inhibitoreffekt gewissen elektrochemischen Reaktionen gegenüber gegründet. So ist es möglich, diesen Substanzen mit einer guten Genauigkeit (2–3%) bei Konzentrationen von ungefähr 10⁻⁶M zu dosieren.     

In Process Citation

The products of hydrolysis of tetrahydrozoline [2-(1,2,3,4-tetrahydro-1-naphthyl)-2-imidazoline] have been isolated by thin-layer chromatography and identified by ultraviolet and infrared spectroscopic analysis. Their structure has been well established by use of mass spectrometry and a degradation scheme advanced. Alkaline hydrolysis opens the imidazoline ring to give an amide compound which undergoes further hydrolysis, in acid solution, to 1,2,3,4-tetrahydronaphthoic acid and ethyl-enediamine.