Solid dispersions materials

Livering The progressive, irreversible increase in consistency of a pigment-vehicle combination. Livering in the majority of cases arises from a chemical reaction of the vehicle and the solid dispersed material, but it may also result from polymerization of the vehicle. 

Cl2C = CCl CCl =CCl2. Colourless viscous liquid b.p. 210-211 C. Principally used as a dispersant material for obtaining i.r. spectra of solids in mulls. Skin irritant. 

In general, when sepiarating two liquids, they must be immiscible and have different spiecific gravities before a separation technique-such as oil/water separation-would be effective. In the case of finely dispersed liquids or finely dispersed solids, if the dispersed material is below one micron in particle size, centrifuging should be considered. The use of centrifugal force on the differing densities of the material can facilitate the separation technique. 

Consequently the absolute potential is a material property which can be used to characterize solid electrolyte materials, several of which, as discussed in Chapter 11, are used increasingly in recent years as high surface area catalyst supports. This in turn implies that the Fermi level of dispersed metal catalysts supported on such carriers will be pinned to the Fermi level (or absolute potential) of the carrier (support). As discussed in Chapter 11 this is intimately related to the effect of metal-support interactions, which is of central importance in heterogeneous catalysis. 

A brown explosive form is produced if excess sodium is used in preparation of thiophene homologues—possibly because of sulfur compounds [1], As normally produced, it is a dry stable solid, but material prepared from acetylene and sodium-oil dispersions ignites in air [2],... 

Addition of sodium hydride to a damp reactor which had not been pinged with inert gas caused evolution of hydrogen and a violent explosion. Solid dispersions of the hydride in mineral oil are more easily and safely handled [1], When an unprotected polythene bag containing the hydride was moved, some of the powder leaked from a hole, contacted moisture and immediately ignited. Such materials should be kept in tightly closed containers in an isolated, dry location [2],... 

Most examples discussed so far made use of amorphous inorganic supports or sol-gel processed hybrid polymers. Highly disperse materials have recently become accessible via standard processes and, as a result, materials with various controlled particle size, pore diameter are now available. Micelle-templated synthesis of inorganic materials leads to mesoporous materials such as MCM-41, MCM-48, MSU, and these have been extensively used as solid supports for catalysis [52]. Modifications of the polarity of the material can increase the reactivity of the embedded centre, or can decrease its susceptibility to deactivation. In rare cases, enhanced stereo- or even... 

In matrix solid-phase dispersion (MSPD) the sample is mixed with a suitable powdered solid-phase until a homogeneous dry, free flowing powder is obtained with the sample dispersed over the entire material. A wide variety of solid-phase materials can be used, but for the non-ionic surfactants usually a reversed-phase C18 type of sorbent is applied. The mixture is subsequently (usually dry) packed into a glass column. Next, the analytes of interest are eluted with a suitable solvent or solvent mixture. The competition between reversed-phase hydrophobic chains in the dispersed solid-phase and the solvents results in separation of lipids from analytes. Separation of analytes and interfering substances can also be achieved if polarity differences are present. The MSPD technique has been proven to be successful for a variety of matrices and a wide range of compounds [43], thanks to its sequential extraction matrices analysed include fish tissues [44,45] as well as other diverse materials [46,47]. 

Colloidal suspensions, emulsions and solid dispersions are produced by means of colloid mills or dispersion mills. Droplets or particles of sizes less than 1 (im may be formed, and solids suspensions consisting of discrete solid particles are obtainable with feed material of approximately 100-mesh or 50 p,m in size. 

In DSC the sample is subjected to a controlled temperature program, usually a temperature scan, and the heat flow to or from the sample is monitored in comparison to an inert reference [75,76], The resulting curves — which show the phase transitions in the monitored temperature range, such as crystallization, melting, or polymorphic transitions — can be evaluated with regard to phase transition temperatures and transition enthalpy. DSC is thus a convenient method to confirm the presence of solid lipid particles via the detection of a melting transition. DSC recrystaUization studies give indications of whether the dispersed material of interest is likely to pose recrystallization problems and what kind of thermal procedure may be used to ensure solidification [62-65,68,77]. 

Matrix solid-phase dispersion techniques have also been suggested for the determination of aminoglycoside residues in bovine tissues (19, 20). The solid-phase material employed in these methods was a cyanopropylsilyl (CN) sorbent. 

CA 69, 98129w(1968) [Conditioning particulate materials for use in org expls, is described. Solid pulverulent materials (such as RDX, PETN or AN) suitable for suspension in melted org expls (such.as TNT) were treated before dispersion, to make them wet and disperse better, with.= 1 liq or solid org Si compd (such as methylchloro-silane of the general formula R1R3R3R4Si,... 

Nucleants. Although nylons crystallize quickly, it is often an advantage, particularly for small parts, to accelerate this process to reduce cycle time and increase productivity. Nylon-6, which crystallizes more slowly than nylon-6,6, also benefits from nudeation in unreinforced formulations. Nucleants are generally fine-particle-size solids or materials that crystallize as fine particles before the nylon. The materials, eg, finely dispersed silicas or talc, seed the molten nylon and result in a higher density of small uniformly sized spherulites in nylon-6 the crystalline form is also changed. Nudeation increases tensile strength and stiffness but makes the material more britde. Mold shrinkage is lower for nudeated resins. 

Reacted materials, such as hydious calcium silicate, are made with the solids dispersed to create density on the order of 12 Ib/lV I02 kg/rir i and still provide high compressive strength. While the reflectance ami emitlanec til the solid phase have an effect on heat transfer, it is the still air within the mass that gives it significant thermal resistance,... 

Other methods to prepare solid micelle dispersion, such as spray drying of a drug containing micelle solution onto solid core materials or solvent emulsiLcation technique to prepare solid lipid nanoparticles, can be found in literature (Karmazina, 1997 Burruano et al., 1999 Luo et al., 2006 Radomska-Soukharev et al., 2006). 

Various techniques available for characterization of solid-state properties of raw materials and Ln-ished solid dispersions are presented in this section. In most cases, solid dispersions are process into Lnished dosage forms using conventional approaches such as tabletting, encapsulation, and < forth, and the characterization of such Lnished dosage formulations are not presented here. 

API material characterization before manufacturing for potential impact assessment. Process understanding and evaluation of specialized technologies [twin-screw wet granulation (TSWG), extrusion, solid dispersion, etc.] for long-term resolution... 

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