Multicomponent preparation

Scheme 32. Multicomponent preparation of protected expanded [n]pericyclinones...

Gradient Elution Conditions in Multicomponent Preparative Liquid Chromatography. 

Identity tests (physical, chemical, chromatographic eind, if possible, a copy of the chromatogram). For multicomponent preparations, the most important ingredients cim be identified through the use of fingerprints obtained by thin-layer or high-performance liquid chromatography. 

Caffeine is often present in pharmaceutical preparations in combination with other drugs, such as acetyl salicylic acid, phenacetin,antipyrin, etc. Because classical analytical techniques (e.g. spectrophotometric and colourimetric methods) can be quite time consuming and leave much to be desired in accuracy and precision, gas chromatography has been quite extensively applied for the analysis of such multicomponent preparations. 

Jacob et al. used the method of characteristics to discuss the general properties of the system of mass balance equations in multicomponent preparative gas chromatography (GC) [34-36], assuming either a linear or a nonlinear isotherm. The GC problem is more complicated than the HPLC one because the gas mobile phase is much more compressible than a solution and the mobile phase velocity is very different inside and outside a high concentration band because the partial molar volumes of compounds are much larger in the gas mobile phase than in the condensed stationary phase (the sorption effect). They showed that the method of characteristics appHes to multicomponent systems as well as to single component... 

The foregoing discussion has focused upon condensations of non-enolizable aldehydes and ketones to afford green processes and products. That approach was extended to include a one step multicomponent preparation of N-mono-substituted or N,N-disubstituted aniline derivatives (Scheme 6.2). The... 

Just as in ultraviolet-visible spectrophotometry, derivative techniques have also been applied to the analysis of fluorescent substances in multicomponent preparations. The advantages here are reported to be the enhanced spectral resolution and amplification of signal that manifests with substances exhibiting narrower spectral bands. Derivative spectrofluorimetric techniques have been applied, for example, to the determination of chlorpromazine sulfoxide in chlorpromazine hydrochloride preparations. 

Synchronous scanning techniques have also been applied to the quantitative analysis of fluorescent substances. Synchronous scanning involves scanning both the excitation and emission monochromators simultaneously, while maintaining a constant wavelength interval between them. The technique has been employed in the analysis of multicomponent preparations. The technique is reported to simplify the spectra of multicomponent samples and reduce the bandwidths of fluorescence spectra. The equation relating the measured fluorescence to concentration is given by... 

Kaczmarski, K. and Antos, D. (1996) Modified Rouchon and Rouchon-like algorithms for solving different models of multicomponent preparative chromatography. /. Chromatogr. A, 756, 73-87. 

Preparations for cutaneous (or dermal) application may be used for local treatment as well as for transdermal administration with a systemic effect. The chapter focuses on preparations with a local effect and on design of formulation and method of preparation of those prepared in pharmacies. The interaction between skin, active substance and base, the anatomy of the skin and biopharmaceutical aspects of cutaneous preparations are discussed as well as the therapeutic effect of the base. Because of the important role of the pharmacist in prescription assessment some recommendations for the communication with the physician are given. One aspect is how to proceed with a request for the mixing of two licensed medicines or for the addition of an active substance or an excipient to a licensed product. The formulation design is generally following the several phases of the multicomponent preparations. Based on the... 

M. J. Aliaga, D. J. Ramon, M. Yus, Org. Biomol. Chem. 2010, 8, 43. Impregnated copper on magnetite an efficient and green catalyst for the multicomponent preparation of propargylamines under solvent free conditions. 

For other example of a multicomponent preparation of spiroindolines, see L. El Kaim, L. Grimaud, X.-F. Le Goff, M. Menes-Arzate, L. D. Miranda, Chem. Commun. 2011, 47, 8145-8147. Straightforward four-component access to spiroindolines. 

A new salicylate eledrode based on polymer membranes was used in a flow injection analysis system [66]. The electrode membrane contains 29.2-31.0% of PVC, 5.8-6.3% of tetraoctylammonium salicylate, 58.5-62.7% of o-nitrophenyloctylether and 6.5% of p-ferf-octylphenol. The tubular electrode was stored for approx. 6 months in a sodium salicylate solution. The electrode shows the slope of response curve close to theoretical — 56.0 0.6 mV decade in the range of 5 x 10" -10" mol L the response time is up to 5 s. The electrode can be used in a pH range of 6-9. The log K selectivity coefficients are 2-2.9 for acetates, 1.8-2.2 for chlorates, 0.7-1.0 for nitrates and 0.6-1.3 for acetosalicylates. The tubular salicylate electrode can be used for determination of acetylsalicylic add, after its previous analysis to salicylate, in multicomponent preparations and effervescent tablets (Anadin Extra, Aspirin, Dolviran, Alka-Seltzer). The results of potentiometric measurements are consistent with the method used in pharmacopoeia 100.7 to 103% of the compound was obtained, with standard deviation of RSD 0.6-1.8%. 

The main problem in sample preparation is related to the quantitative recovery of steroids 6om single or multicomponent preparations. Steroids are used therapeutically in most pharmaceutical formulations, including tablets, oily or aqueous injections, capsules, suppositories, creams and ointments. In most cases, sample preparation is not a serious problem. Problems can arise when side reactions occur during extraction. For example. Vitamins D are considered very sensitive compounds among the steroids. They are sensitive to atmospheric oxygen, traces of acids and bases, light, heat, etc. To avoid decomposition during the sample preparation and to obtain reproducible results some precautions are recommended (10) ... 

Another one-pot multicomponent preparation of pyrrole was successfully achieved via condensation of 3-(bromo-acetyl)coumarin, acetylacetone, and variety of amines in aqueous PEG 400 (Scheme 29) [53]. A number of catalysts were screened and alum was found to be the most efficient. The highest yield of 52 was obtained in aqueous PEG 400 with the water PEG 400 ratio equal to 2 3. Other solvents were found to give lower product yields. Using water or PEG 400 as a sole solvent decreased the yield from 91% to 35% or 48%, respectively. X-ray crystallography of one of the compounds 52 (R =H, R2=4-C1C5H4) was used to confirm the structure of these interesting products. 

Prepare a single multicomponent working standard from the stock standards by making appropriate dilutions with methanol. Concentrations in the working standards should be at such a level that a 20- xL sample added to 100 mL of water gives a calibration standard whose response for each trihalomethane is within 25% of that for the samples to be analyzed. 

Multicomponent sol—gel fibers have been successfuUy developed (1,52). The early stages of sol formation and gelation are cmcial for controlling the fiber microstmcture. Aluminosilicates, zirconates, and aluminates (1,18,52) can be prepared by sol—gel methods. MuUite [55964-99-3] 3AI2 O3 -2Si02, fibers... 

Synthetic polymers have become extremely important as materials over the past 50 years and have replaced other materials because they possess high strength-to-weight ratios, easy processabiUty, and other desirable features. Used in appHcations previously dominated by metals, ceramics, and natural fibers, polymers make up much of the sales in the automotive, durables, and clothing markets. In these appHcations, polymers possess desired attributes, often at a much lower cost than the materials they replace. The emphasis in research has shifted from developing new synthetic macromolecules toward preparation of cost-effective multicomponent systems (ie, copolymers, polymer blends, and composites) rather than preparation of new and frequendy more expensive homopolymers. These multicomponent systems can be "tuned" to achieve the desired properties (within limits, of course) much easier than through the total synthesis of new macromolecules. 

Conducting Polymer Blends, Composites, and Colloids. Incorporation of conducting polymers into multicomponent systems allows the preparation of materials that are electroactive and also possess specific properties contributed by the other components. Dispersion of a conducting polymer into an insulating matrix can be accompHshed as either a miscible or phase-separated blend, a heterogeneous composite, or a coUoidaHy dispersed latex. When the conductor is present in sufftcientiy high composition, electron transport is possible. 

There are several approaches to the preparation of multicomponent materials, and the method utilized depends largely on the nature of the conductor used. In the case of polyacetylene blends, in situ polymerization of acetylene into a polymeric matrix has been a successful technique. A film of the matrix polymer is initially swelled in a solution of a typical Ziegler-Natta type initiator and, after washing, the impregnated swollen matrix is exposed to acetylene gas. Polymerization occurs as acetylene diffuses into the membrane. The composite material is then oxidatively doped to form a conductor. Low density polyethylene (136,137) and polybutadiene (138) have both been used in this manner. 

Chromatography Chromatography is a sorptive separation technique that allows multicomponent separations in both gas and Hquid phase. As a preparative tool, it is often used as a displacement-purge process, although many applications employ an inert-displacement mode, especially for use in analysis. General characteristics and operating modes are discussed in a separate part of this section. 

Certain disadvantages of this method of analysis should be enumerated. The preparation of standards becomes a major task if a large variation in concentrations of multicomponent samples is expected. The cost of preparing standards for expensive elements is a major consideration however, recovery and purification are possible. 

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