Carrier compound

The active component of a carrier formulation is generally a nonionic compound of Mr 150-200 containing a benzenoid ring system. A comprehensive review listed the classes of compounds used together with their general properties, ideal requirements and the mechanisms that have been proposed for carrier action [115]. Carrier compounds fall into four main classes phenols, primary arylamines, aryl hydrocarbons and aryl esters. Major... 

Over the last decade the use of carriers has declined markedly and continues to do so, essentially for health, safety and environmental reasons [118-121]. In some countries these products are now virtually banned. Nearly all carrier compounds exhibit all or some of the following toxicity, physiological irritancy or poor biodegradability (Table 12.7). Typical pollution loads for comparable high-temperature and carrier methods are given in Table 12.8. 

Formulations of chlorpyrifos include emulsifiable concentrates, wettable powders, granules, pellets, microencapsulates, and impregnated materials. Suggested diluents for concentrates include water and petroleum distillates, such as kerosene and diesel oil. Carrier compounds include synthetic clays with alkyl/aryl sulfonates as wetting agents (Table 14.1). Little information is available to assess the influence of various use formulations on toxicity, dispersal, decomposition, and bioavailability. Chemical and other properties of chlorpyrifos are summarized in Table 14.2 and Figure 14.1. 

The carrier compounds were useful for identifying the corresponding astatine derivatives by means of paper chromatography (112) and TLC (114)-, the P- and a-activities of and At products, respectively, were measured. 

In a technique known as medical imaging, tracers are used in medicine for the diagnosis of internal disorders. Small amounts of a radioactive material, such as sodium iodide, Nal, which contains the radioactive isotope iodine-131, are administered to a patient and traced through the body with a radiation detector. The result, shown in Figure 4.11, is an image that shows how the material is distributed in the body. This technique works because the path the tracer material takes is influenced only by its physical and chemical properties, not by its radioactivity. The tracer may be introduced alone or along with some other chemical, known as a carrier compound, that helps target the isotope to a particular type of tissue in the body. 

From the biomedical viewpoint, the main consideration prior to administering this a emitter is the possible damage to healthy tissues. Obviously, the more selective and localized is the accumulation of 211At-labelled compound in the tumour bearing tissues ( tumour-binding specificity ) and the more stable is the bond between astatine and the tumour specific carrier compound the better are the chances of therapeutic efficacy. The last decade has seen major efforts to achieve this aim by cooperation of chemists, biologists and physicians. 

Type 2 facilitation is also known as carrier facilitated transport, since a carrier compound, that is, an extractant or complexing agent, solubilized in the organic phase is used to assist transfer across the membrane. In this simation, the solute of interest reacts with the carrier to form a complex that is only soluble in the membrane phase. The solute is de-complexed by a stripping solution contained in the internal phase. An example of such a process is the removal of a metal ion such as copper or zinc from wastewater by the extractant DEHPA (di-2-ethyUiexyl phosphoric acid, represented as HE) as shown in Figure 25.2. In this case, the carrier also enhances the selectivity as most extractants are specifically designed to extract particular metal ions... 

Other structures may exist owing to interactions between the drug and carriers. Ford addresses the following systems glass solutions and glass suspensions, amorphous precipitations in a crystalline carrier, compound or complex formation, and combinations of these systems. 

The values of the stability and rate constant for all the carrier compounds with Na+ studied so far are listed in Fig. 18. For comparison. 

Drug-carrier complexes may be antigenic for both T and B cells. Stimulation and proliferation of dmg-specific T cell clones (sensitization) may provide help for the generation of a separate, B cell immune response to the hapten-carrier compound. 

PLA is a non-toxic and biodegradable material that is extensively used in coating membranes [10] and as carrier compounds [11-18]. The application of PLA in controlled drug-delivery systems is often limited due to its poor wettability. It has... 

FIGURE 17.7 Computer-simulated distributions of the 140 carrier components and the three dyes for the pH 5-8.5 gradient system after 10, 1000, and 10,000 min of constant voltage application. The numbers refer to the pi values of the dyes and the arrowheads mark their locations. Successive graphs are presented with a y-axis offset of 30 mM. The insets a and b depict the concentration profiles of the pi 6.6 and 7.4 amphoteric dyes and the pH profiles, respectively, at the indicated time points. Simulations were performed with Ax = 50 xm and having column ends that are impermeable to any sample and carrier compounds. (Modified from Mosher, R.A. and Thormann, W., Electrophoresis, 23, 1803, 2002. With permission.)... 

Application of direct current voltage induces injection of electrons and holes at cathode and anode producing radical anions and radical cations, respectively, and their recombination excites the EL compound. The injected charges are transported by hopping between the carrier compounds at a high voltage of 10 V cm . The carrier mobility is not high, around 10 10 cm V s , but the time needed to reach the recombination layer is very short, about 10 s, because of the thin layer of around 100 nm, so that the response of the device is very quick [113]. 

The results of the characterization of extrusion behaviour are explained using ceramic catalyst carrier compounds based on y-aluminium oxide. The solid phase of all compounds was the same, consisting of y-aluminium oxide and pseudobohmite in a ratio of 2 1. 

Historically, chromizing was first achieved by Kelley [141] in the form of a cementation process, but a major disadvantage inherent to his method was the high temperature (1300°C) required. Weber [142] and Marshall [143] overcame this problem by using a halogen carrier compound, the function of which was to provide a volatile source of chromium at the substrate surface. By this means, temperatures were reduced to the order of 1000°C. The various processes that have been devised for chromizing metals by vapor deposition may be summarized as follows ... 

Uses Binder, carrier, compounding agent, dispersant, stabilizer, protective colloid in polymerization textiles paper adhesives cement/plas-ter additive peelable caulks ceramics strippable coatings mold release nonwovens Trade Names Airvol 205... 

Promising results have been obtained with the facilitated transport membranes in which an oxygen-complexing carrier compound acts like a shuttle to transport the oxygen selectively throngh the membrane [44],... 

Because the actual amounts of radioactive materials used in normal laboratory experiments are usually very small a chemical carrier is added. This is a nonradioactive isotope of the radioactive material. This allows conventional chemical operations like precipitation. Care must be taken that the carrier compound is chemically identical to the compound of the radionuclide or equilibrates with the chemical species of the radioactive material. 

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