Emulsion multiple de type L/H/L: étude de l'obtention et du mécanisme de libération.

Synopsis An O/W/O multiple emulsion was formulated using almond oil as the inner phase and liquid paraffin as the outer phase. The properties of the formulation ingredients were explored: effect of the type of primary emulsifier, and the nature and concentration of the secondary emulsifier. The volume fraction of the internal phase in the multiple emulsion was also optimized with regard to the stability. The multiple systems were assessed by evaluating several parameters such as the macroscopic aspect, the droplet size, the direction of the dispersion and the accelerated stability under centrifugation or elevated temperature. The effect of some additives (ozokerite, benzyl alcohol and glycerol) was examined. Whatever additive was used, a decrease in the formulation stability, which could be attributed to different phenomena, was observed. Furthermore, an analytical procedure was developed for studying the release of an active principle, alpha-tocopherol (vitamin E). This release could be a result of the instability of the multiple droplets or a diffusion through the water layer membrane. This procedure was based on the difference of chemical type between the two oil phases: mineral outer phase and fatty inner phase. Two chromatographic methods were used: a gas chromatographic assay of oleic acid which is the main component of the fatty phase, and a liquid chromatographic assay for the alpha-tocopherol, encapsulated in the inner phase. The presence of oleic acid in the paraffin phase originated from a rupture of the multiple droplets, whereas the presence of alpha-tocopherol in the outer phase could be due both to a diffusion phenomenon and to the instability of the formulation. The results obtained showed that only the rupture of the droplets occurred. Moreover, a part of the alpha-tocopherol was retained by Hypermer A 60 used as an emulsifier in the formulation.

[Rapid analysis of plastic materials for pharmaceutic use]. / Analyse rapide des matières plastiques à usage pharmaceutique.

The use of plastic materials as containers for pharmaceuticals implies the knowledge of previous data and the constancy of their composition. These data and migration studies are acquired in the development phase and are the ground line in routine control. The molecular size distribution and the identification of principal additives are determined by gel permeation chromatography. Infra red spectrometry is applied to the determination of relative proportions of monomers in copolymers; HPLC and GLG head space are suitable for the identification of additives and for the studies of stability.

[Not Available]. / Degradation oxydative des sulfamides a usage therapeutique Isolement structure et methodes d'analyse des produits formes.

The mild oxidation of bactericidal sulphonamides by hydrogen peroxide in acidic medium at room temperature in daylight, is reported. The oxidation products have been isolated by classical chromatography and purified, and their purity has been determined by HPLC. They have been identified by spectroscopy, chiefly by infrared and mass spectroscopy. An oxidation product not previously reported has been isolated and identified. An oxidation mechanism and the kinetics are discussed.

[Not Available]. / Dosage des acides faibles en milieu ammonium quaternaire concentre.

The determination of weak acids in concentrated quaternary ammonium salt medium is proposed. In this type of solvent, which has few hydrogen bonds, complexation arises through homoconjugation or heteroconjugation in the presence of weak acids or bases; this enhances the acidity of the conjugate acid-base couples and makes them directly titratable. The procedure is applicable to determination of theobromine and theophylline with silver nitrate in concentrated tetrabutylammonium acetate medium. These compounds are titrated as weak acids and not as their conjugate bases.

[Not Available]. / Action des rayonnements beta et des oxydants sur le di-tert. butyl- 3,5 hydroxy-4 toluene.

An HPLC method for the identification and determination of BHT (3,5-di-tert.butyl-4-hydroxytoluene) and the by-products obtained from it by beta-ray or oxidative treatment is described. The chemical structure of the by-products is established by mass spectrometry. The irradiation leads to the dimeric and trimeric forms of the antioxidant and the oxidation to a cyclohexa-2,5-dien-1-one with substitution of a hydroxy and a methanol or aldehyde group at position 4.

[Not Available]. / Action de l'acide citrique sur l'anhydride acetique et la pyridine Determination du mecanisme reactionnel et de la structure du compose forme.

This study outlines the structure of the coloured by-product obtained by the action of citric acid on acetic anhydride and pyridine. The methods used are (13)C nuclear magnetic resonance, infrared spectrometry and mass spectrometry. The reaction scheme proposed indicates that the compound is pyridinium aconitate. The chemical structure is corroborated by mass spectrometry.

[Not Available]. / Etude analytique du Goodrite 3114, antioxydant des polyolefines: comportement vis a vis des agents de sterilisation.

An HPLC method for the identification and determination of Goodrite 3114 and of the product derived from it by gamma-ray irradiation is described. The chemical structure of the by-product obtained by the gamma-irradiation has been established. A technique for research on migration phenomena is proposed.

Nuclear magnetic resonance spectrometry and liquid chromatography of two bile acid epimers: ursodeoxycholic and chenodeoxycholic acid.

A specific reverse-phase high-performance liquid chromatographic (HPLC) technique is described for the analysis of bile acids and their conjugates in human serum. Precise quantitation is obtained using UV detection. 13C-NMR spectrometry suggests a structural explanation for the different HPLC retention times of chenodeoxycholic acid, its epimer (ursodeoxycholic acid), and their methyl esters.

[Not Available]. / Action de l'acide ascorbique sur les amines primaires et les acides alpha amines.

This study outlines the structure of the by-product obtained by the action of ascorbic acid on primary amines and alpha-amino-acids; the methods used are (13)C, NMR and infrared spectrophotometry. The chemical form is comparable to that of Ruhemann purple, obtained by the action of ninhydrin on alpha-amino-acids.

[Not Available]. / Identification et dosage des sels biliaires et de leurs derives conjugues en chromatographie liquide.

Detection and determination of bile acids and their glycine- and taurine-conjugated derivatives are realized by reversed-phase liquid chromatography either directly or after ion-pair formation. Operating conditions and the relation between capacity factors and structure are investigated. The determination of bile acids extracted from biological samples is possible by these techniques.