Volatilization, controlled release

The organophosphoms ester dichlorvos is sufficiently volatile to be incorporated either in permeable plastic bottles or plastic strips which permit its controlled release for fumigation of cupboards and closets to control cockroaches, or as flea collars on pets. 

The dioxolanones 33 <95JAP07291959> and 34 <95JAP07285960> are both reported to be useful as solvents, while 35 has been used as an X-ray contrast medium <96MIP19487>. Carboxydioxolanes such as 36 are useful for controlled release of volatile aldehyde pheromones <96JCR(S)274> and pharmaceutically active amines R2NH can be administered in... 

Abstract Progress that has been made in research on the chemical aspects of mammalian semiochemistry over the past decade is discussed on the basis of examples from the most topical problem areas. The chemical characterization of the volatile organic constituents of the urine, anal gland secretions and exocrine gland secretions of rodents, carnivores, proboscids, artiodactyls and primates, and their possible role in the semiochemical communication of these mammals are discussed, with particular emphasis on the advances made in the elaboration of the function of proteins as controlled release carrier materials for the semiochemicals of some of these animals. 

An animal can control release of odor molecules from body surfaces, especially skin gland areas, up to a point. But in moist air, volatiles from secretions on skin or hair will evaporate more easily. If only intermittent odor emission is desirable, humidity would interfere with the animal s odor release. Glands that produce such intermittent signals, such as alarm odors, appear to be more developed in species or subspecies in drier climates. An example is the metatarsal gland in... 

A fermented-egg product (FEP), patented as an attractive bait for synanthropic flies, has been shown to be attractive to coyotes and repellent to deer (79). Its components are variable, with relative concentrations of 77% fatty acids, 13% bases, and 10% (primarily) neutrals composed of at least 54 volatiles such as ethyl esters, dimethyl disulfide, and 2-mercaptoethanol. Synthetic formulations have been evaluated to find a replacement for a patented fermented-egg protein product that attracts coyotes and repels deer. Ten aliphatic acids (C-2 to C-8), four amines (pentyl, hexyl, heptyl, and trimethyl), dimethyl disulfide, 2-mercaptoethanol, and 54 more volatiles (C-l to C-5 esters of C-l to C-8 acids) have been tested as synthetic fermented egg (SFE) (80) in approximately the same proportions that are present in FEP. Weathering was a problem that caused decreased efficacy, which suggests trials of controlled-release formulations. Fourteen repellents have been examined against white-tail deer in Pennsylvania in choice tests when treated onto shelled com (81). 

Malone, M.E., Appelqvist, I.A.M. (2003). Gelled emulsion particles for the controlled release of lipophilic volatiles during eating. Journal of Controlled Release, 90, 227-241. 

Measurement of Volatile Matter Release Rates. Volatile matter release rates from anthracite were determined by using the apparatus shown diagram-matically in Figure 1. The power input to the 1-kw., 20-volt Hoskins tube furnace and transformer was controlled by means of a Leeds Northrup durationadjusting type program controller which permitted linear heating rates up to 20°C. per min. to be selected with varying soak times and temperatures. A maximum temperature of 1000°C. was used since this was the maximum temperature at which the furnace could be operated continuously. The temperature of the furnace was measured by a chromel-alumel thermocouple inside a... 

In an attempt to provide further information relative to the validity of the diffusion mechanism, a typical set of results was selected from the isothermal release work, and the volume of volatile matter released was plotted against the square root of time. For a pure diffusion process such a plot should be almost linear initially (4) whereas for a true logarithmic time law, dVt/dt should tend to infinity for very small values of t. Figure 12 shows that by this criterion the rate controlling mechanism appears to be diffusion and not chemisorption. The fact that the curve does not pass through the origin is undoubtedly caused by the fact that it was not possible to heat the sample to... 

Herrmann, A. (2007) Controlled release of volatiles under mild reaction conditions from nature to everyday products. Angewandte Chemie, International Edition, 46, 5836-5863. 

The main use of PVC is for intravenous bags. However, PVC has been used in the controlled release of volatile insecticides, herbicides, pheromones, and perfumes by diffusion through a PVC membrane of multilaminated stripes. A monolithic matrix device of PVC can be prepared by mixing PVC particles with a suitable plasticizer and an active agent, followed by heating of the mixture in a mold. A solid PVC matrix is obtained from the subsequent cooling. 

In order to extrapolate the laboratory results to the field and to make semiquantitative predictions, an in-house computer model was used. Chemical reaction rate constants were derived by matching the data from the Controlled Mixing History Furnace to the model predictions. The devolatilization phase was not modeled since volatile matter release and subsequent combustion occurs very rapidly and would not significantly impact the accuracy of the mathematical model predictions. The "overall" solid conversion efficiency at a given residence time was obtained by adding both the simulated char combustion efficiency and the average pyrolysis efficiency (found in the primary stage of the CMHF). 

Major Disadvantages Of Residue Analysis. In the foregoing discussion several advantages and disadvantages of the various methods have been discussed, but the most severe limitation of the residue analysis methods has not been touched upon. That disadvantage is that none of these methods provide any direct information about either the quality or quantity of the material actually released. If volatile degradation products are produced, this information would not be detected nor would the ratio of components actually released be directly measurable. Since the material released is the active ingredient of any controlled release system, this lack of information is a serious drawback to dependence on residue analysis for release rate determinations. 

In 1980, we reported the structure of the Comstock mealybug, Pseudococcus comstocki (Kuwana), pheromone as 2,6-dimethyl-l,5-heptadien-3-ol acetate (24, 25) and in 1981, we identified the pheromone of the citrus mealybug, Planococcus citri (Risso), as (lR-cis)-(+)-2,2-dimethyl-3-(l-methylethenyl)cyclobutanemethanol acetate (26). Both of these pheromones have been synthesized and are currently being used as baits in monitor traps in California and Texas. These compounds are more volatile than the pheromones for most other insects and therefore formulations for controlled release need to be modified from those described earlier. 

Herrmann A, Giuseppone N, Lehn J-M (2009) Electric-field triggered controlled release of bioacive volatiles from imine-based liquid crystalline phases. Chem Eur J 15 117-124... 

In this review dealing with recent advances in membrane science, the term membrane" will be used to indicate any medium which acts as a barrier to transport into or out of a region, provides selective transfer of one species over another or regelates the transport of a material to its environment at a controlled rate. In addition to the common usage of the word membrane" to indicate a dense polymer film, the above definition includes a variety of interesting cases such as highly porous ultrafiltration membranes and hydrophobic liquid membranes with selectivity properties which can be tailored by incorporation of materials which selectively complex with one of the species to be processed. The important topics of controlled release of chemicals from polymeric devices and removal of volatile monomers from addition polymers such as poly (vinyl chloride and poly (acrylonitrile are also treated here. 

Pervaporation is now being introduced in waste management technologies, but the application of the process is of an indirect nature [ 26 1. One of these uses involves elimination of compounds from a liquid mixture. In this procedure, only high-volatility components are separated. It should be noted that such compounds are usually toxic in nature, and a controlled release is a matter of prime importance not only to technologists, but to environmentalists as well. 

For volatile compounds, releasing analytes into the headspace is relatively easy because they tend to vaporize once they are dissociated from the matrix. For semi-volatile compounds, the low volatility and relatively large molecular size may slow down the mass transfer from the matrix to the headspace and, in some cases, the kinetically controlled desorption or swelling process can also slow down the extraction. 

The fine adjustments are made using a feedback control system. An important element of that system is an optical sensor which is used to control the hydrocarbon emissions. As more volatiles are released into the furnace, the sensor detects the... 

Only the thermal process is capable of yielding isotropic microporous structures in thick sections. Wet and dry processes tend to become increasingly anisotropic as the thickness of the membrane gel is Increased. This unique property renders thermal process gels ideally suitable for use in controlled release applications. The gels can be cooled, ground up, extracted and filled with volatile insect repellents, for example. 

Microencapsulation of flavors is a technology of enclosing flavor compounds (core materials) in a carrier matrix. An amorphous or metastable solid is normally used as a carrier matrix. Microencapsulation is useful for improving the chemical stability of flavor compounds, providing controlled release of flavor compounds from microencapsulated flavor products, providing a free-flowing powder with improved handling properties and physical protection of volatile properties of flavor. 

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