Radicalar probes to measure the action of energy on granular materials

International audienceMeasuring the action of energy on matter is a complex problem, especially in the case of granular materials. For example, particle size reduction by grinding generally shows poor overall energetic yields and a significant challenge in this area is to accurately estimate the energy consumed, including that stored in the particles. Fine or ultra-fine grinding processes require a lot of energy, part of which becomes internal energy and can lead to mechanochemical reactions and useful products. We studied the appearance of free radicals during the grinding of a-lactose monohydrate by means of electron spin resonance (ESR). These radicals are the same as those induced by gamma-radiation and comparison of ESR spectra intensities with those from ground products allows the determination of an `equivalent gamma-irradiation dose'. This gives a novel concept for characterizing the action of mechanical energy on matter in fine grinding by using molecular probes. This is the first example of the investigation of mechanochemical energy during the fine grinding process

Use of co-grinding as a solvent-free solid state method to synthesize dibenzophenazines

International audienceMany synthetic methods exist for dibenzoquinoxalines but only a few for dibenzophenazines and their aza derivatives and even less are `green'. Some dibenzophenazines and dibenzopyridoquinoxaline have been efficiently obtained with good to excellent yield by a very simple method which does not require use of solvent or catalyst. Solid phase synthesis using co-grinding presents thus many advantages in developing greener synthetic organic pathways. (C) 2011 Elsevier Ltd. All rights reserved

Modeling the mean interaction forces between powder particles. Application to silica gel-magnesium stearate mixtures.

International audienceDry coating experiments were performed by using the Hybridizer (Nara). Large host silica gel (SG) particles (d50 = 55 μm) were coated with fine invited particles of magnesium stearate (MS, d50 = 4.6 μm) for different contents of MS in the mixture. The real MS mass fraction wI obtained after mechanical treatment has been determined thanks to calibration from TGA measurements. The surface structure and morphology of MS coatings were observed using Environmental Scanning Electron Microscopy (ESEM) and Atomic Force Microscopy (AFM) [26, 27]. AFM has been also used to measure the adhesion forces between particles. Interaction forces between the material attached to the cantilever (Magnesium Stearate MS) and the surface of the composite material (Silica Gel SG or Magnesium Stearate MS) have been determined at different surface locations. For different compositions wI of the mixture MS-SG, the numeric distribution and the mean value f of the forces fH obtained for MS-SG interactions or fI for MS-MS interactions have been established and the experimental curve showing the evolution of f versus wI has been derived. Models of ordered structures have been developed, implying morphological hypotheses concerning large spherical or cylindrical host particles H and small invited spherical I. Different types of distribution of I materials onto the surface of H have been considered: for examples a discrete monolayer –or multilayers- of monosized particles I on the H surface. The coordinence of MS particles around SG particles has been estimated to calculate the free SG surface fraction through different modelling and to obtain the mean force f versus composition wI. The theoretical force values have been compared to experimental ones. The deviations have been discussed in terms of guest particle distributions on the surface of the large host particles and morphological hypotheses

Electron spin resonance - thermoluminescence studies on irradiated drugs and excipients

Issu de : 12th International Meeting on Radiation Processing (IMRP-12), AVIGNON, FRANCE, MAR 25-30, 2001International audienceThe methods (ESR, TL, GPC) developed to prove whether or not a foodstuff has been irradiated can be used to get the same proof in case of an irradiation treatment of drugs, excipients and cosmetic products

Evolution of the interaction of a new chemical entity, eflucimibe, with gamma-cyclodextrin during kneading process

International audienceThe aim of this study was to enhance the low solubility of eflucimibe, a new chemical entity which can be used as medicine to treat dyslipidemiae, by complexation with gamma-cyclodextrin. The complex was prepared using kneading method. The interaction evolution was studied during process by comparison of the semi-solid and physico-chemical states of the product. The evolution of the semi-solid state was followed by torque measurement when the evolution of physico-chemical state was studied by differential scanning calorimetry, infrared spectroscopy and by determination of the drug solubilisation profile. The interaction, which occurs during the process, is characterised by a modification of the product consistency and by a disappearance of the drug endothermic peaks, a disappearance of a drug spectral band and a widely improvement of the drug solubilisation profile. Indeed, after complete interaction, the drug quantity solubilised in specific conditions increased about 44-fold compared to those of untreated drug. Moreover, the comparison of the physico-chemical and semi-solid states during kneading process clearly shows that when the interaction takes place, a solidification of the paste occurs. The results of these works suggested that the formation of new solid phase allows an enhancement of the solubility of eflucimibe