Mélange

Résumé

vignette|Mélange hétérogène de soufre et de fer. Un mélange est une association de deux ou plusieurs substances solides, liquides ou gazeuses qui n'interagissent pas chimiquement. Le résultat de l'opération est une préparation aussi appelée « mélange ». Les substances mélangées sont étroitement juxtaposées dans un même espace, chacune gardant ses propriétés physiques et chimiques. Les éléments mélangés peuvent être séparés de nouveau par l’action d'un procédé physique. Un mélange est différent d'un corps pur qui ne comporte qu'une seule substance. Typologie On distingue deux grands types de mélanges :

un mélange hétérogène est un mélange dont on peut distinguer au moins deux constituants à l'œil nu ;
un mélange homogène est un mélange dont on ne peut pas distinguer les constituants à l'œil nu.

Voir aussi Articles connexes

Formulation
Mélangeur
Dosage
Procédé

Liens externes *

Source officielle

https://fr.wikipedia.org/wiki/M%C3%A9lange

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Determination of water quality standards for chemical mixtures: Extension of a methodology developed for herbicides to a group of insecticides and a group of pharmaceuticals

Kristin Becker van Slooten, Emmanuel Maillard

Elsevier2008

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Critical issues in using the common mixture toxicity models concentration addition or response addition on species sensitivity distributions: A theoretical approach

Vincent Gregorio

The risk of chemical mixtures to ecosystems is often assessed by applying the model of concentration addition or response addition combined with species sensitivity distribution (SSD) curves. Mixture effect predictions have been shown to be consistent only when these models are applied for a single species, however, and not with several species simultaneously aggregated to SSDs. The more stringent procedure for mixture risk assessment would hence be to apply first the concentration addition or response addition models to each species separately and, in a second step, to combine the results to construct an SSD for a mixture. Unfortunately, this methodology is not applicable in most cases because the large data sets it requires are usually unavailable. Based on theoretical data sets generated, the authors aimed to characterize the difference that can exist between these 2 methodologies. Results show that the use of concentration addition on SSD directly may lead to underestimations of the mixture concentration affecting 5% or 50% of species, especially when substances present a large standard deviation in ecotoxicity data constructing their SSD. The application of response addition can lead to over- or underestimations, depending mainly on the slope of the dose-response curves of the individual species. When assessing the risk of mixtures, one must therefore keep in mind this source of error when applying concentration addition or response addition to SSDs directly. (c) 2013 SETAC

Society of Environmental Toxicology and Chemistry Press2013

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Chemosensors Based on Metal-Dye Complexes for Bioanalytes

Friederike Gundula Marie Zaubitzer

Multicomponent chemosensors were prepared by mixing the rhodium(III) complex [(η5-C5Me5)RhCl 2]2, nickel(II) chloride and/or copper(II) chloride with commercially available dyes in buffered aqueous solution. The sensors were used to detect various biomolecules, which interact with the components of the sensing ensemble and alter the composition, and hence the color of the sample. The sensors were analyzed by UV/Vis spectroscopy. A mixture of [(η5-C5Me5)RhCl 2]2, three dyes and pyrophosphate was employed to determine in retrospect the time at which the target molecules ADP and ATP were added to the sensing ensemble. An artificial neural network was used to correlate absorbance data with analyte addition times. Dynamic combinatorial libraries of metal-dye complexes prepared from NiCl2, CuCl2 and three dyes were used to distinguish between mixtures of the peptide hormones angiotensin I and angiotensin II. The discriminative power of the sensor was increased by analyzing samples in a time-resolved fashion. Nine primary amines were identified in a sensing ensemble, where amines were first combined with pyridine-2-aldehyde in the presence of NiCl2 or CuCl2, in order to obtain metal-stabilized imine mixtures. A colorimetric output was generated by adding a dye. In an approach to sense conventional sugars in an indicator displacement assay, sugars were transformed in situ into sugar imines prior to the sensing experiment.

EPFL2010

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