Chemical stability photostability

Oral solids Solubility, dissolution, polymorphism, chirality, particle size, powder flow, chemical stability, photostability, compressibility, hygroscopicity, and excipient interactions. 

Oral liquids Solubility, polymorphic conversions, chirality, excipient interactions, chemical stability, photostability, pH effects, and container interactions (e.g., type III glass). 

To our benefit, fluorescence is a well-observed phenomenon characteristic for many materials. This allows providing broad selection of fluorescence reporters that have to be chosen according to different criteria high molar absorbance and fluorescence quantum yield, convenient wavelengths of excitation and emission, high chemical stability, and photostability. They are well-described in other chapters of this book and in other books of these series. As we will see subsequently, they should be adapted to particular technique of target detection and to particular method of observation of fluorescence response, which needs establishing additional criteria for their selection. 

The spectral characteristics of protein conjugates made with Lissamine rhodamine B derivatives are of longer wavelength than those of tetramethylrhodamine—more toward the red region of the spectrum. In addition, modified proteins have better chemical stability and are somewhat easier to purify than those made from TRITC (discussed previously). Lissamine derivatives also make more photostable probes than the fluorescein derivatives (Section 1, this chapter). 

In 1958, Barthel et al. [25] reported dimethrin (15), which was the first substituted benzyl alcohol ester of chrysanthemic acid. This compound was not put into practical use due to its low insecticidal activities. Phenothrin (16), one of the m-phenoxybenzyl alcohol esters developed by Fujimoto et al. [26], was found to have superior chemical stability as well as safety, and has been the sole pyrethroid used as a lice control agent for humans. Further improvement was made by Matsuo et al. [27] who introduced a cyano function at the a position of the benzyl part of phenothrin, leading to a-cyano-m-phenoxybenzyl alcohol esters (17). Thereafter, this alcohol moiety has been used as a component for a number of photostable pyrethroids for agricultural purposes however, the development of cross-resistance can be seen in some pests. 

Also, using dyes as laser media or passive mode-locked compounds requires numerous special parameters, the most important of which are the band position and bandwidth of absorption and fluorescence, the luminiscence quantum efficiency, the Stokes shift, the possibility of photoisomerization, chemical stability, and photostability. Applications of PMDs in other technical or scientific areas have additional special requirements. 

Concerning the chemical stability, oxidation by the ambient oxygen is of major concern [18]. Sealing and encapsulation of the material improves the lifetime. For photostability any absorption process has to be strongly avoided [19, 20]. Not only the linear absorption a0 but also the two-photon absorption a2 is of concern. The prevention of any absorption is therefore not only important for the figures of merit but also for the photostability. 

Parenteral Solubility, micellization, thermal stability, chemical stability, packaging component interaction (glass, stoppers), photostability, physical stress (particularly for protein drugs), buffer interactions, and viscosity. 

Improved stability of the therapeutic agents Encapsulation of the therapeutic agents in the microemulsion structures can offer improvement in the chemical, photochemical and enzymatic stability of the therapeutic agents such as chloramphenicol (chemical stability) [5], arbutin (photostability) [6] and peptides (enzymatic stability)... 

NIR emission, to minimize the tissue absorption and scattering effects. High stability at physiological pH (6.0-7.4), to maintain chemical stability and photostability and resist non-specific binding to serum proteins. 

Just as with organic combustion aerosols, the chemical and physical nature of inorganic solid substrates can have a dramatic impact on the photoreactivity of adsorbed PAH. In 1980, Korfmacher and co-workers reported that BaP, pyrene, and anthracene all pho-tolyzed efficiently in liquid solution but were resistant to photodegradation when adsorbed on coal fly ash. Subsequent studies confirmed this observation and revealed that the carbon content of the ash (and the associated darkening of color) is a key factor in establishing the photostability of these PAHs. Indeed, they were stabilized at relatively small percentages of carbon, e.g., 5% or less (Behymer and Hites, 1985, 1988 Yokley et al., 1986 Dunstan et al., 1989 Miller et al., 1990). 

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