Volatility (chemistry)

Summary

In chemistry, volatility is a material quality which describes how readily a substance vaporizes. At a given temperature and pressure, a substance with high volatility is more likely to exist as a vapour, while a substance with low volatility is more likely to be a liquid or solid. Volatility can also describe the tendency of a vapor to condense into a liquid or solid; less volatile substances will more readily condense from a vapor than highly volatile ones. Differences in volatility can be observed by comparing how fast substances within a group evaporate (or sublimate in the case of solids) when exposed to the atmosphere. A highly volatile substance such as rubbing alcohol (isopropyl alcohol) will quickly evaporate, while a substance with low volatility such as vegetable oil will remain condensed. In general, solids are much less volatile than liquids, but there are some exceptions. Solids that sublimate (change directly from solid to vapor) such as dry ice (solid carbon dioxide)

Official source

https://en.wikipedia.org/wiki/Volatility_(chemistry)

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Encapsulation techniques open up new possibilities to control the kinetics and location of the release of active ingredients. Despite the progresses achieved to obtain a better control over the dimensions and composition of the capsules, the encapsulation of volatile substances is still challenging, even though it is of high relevance especially for the cosmetic industries. One way of encapsulating volatile substances is by kinetically arresting these molecules in a matrix which has a low permeability. A group of materials that likely is well-suited to generate such matrices is composed of small molecules capable of forming crystals.In this thesis, we will investigate the influence of the processing of composites containing small biocompatible organic molecules that serve as matrices with volatile active ingredients on the structure and permeability of the resulting particles. In particular, we will investigate the possibility to use organic salt crystals as matrix materials. Particles of well-defined sizes and compositions will be produced in double emulsions where the influence of the formation kinetics and confinements on the structure and permeability of the particles will be investigated. In addition, we will produce amorphous particles by kinetically suppressing the crystallization reaction using a microfluidic spray-drier. This will be achieved by co-spray-drying the active ingredient with the matrix material. We will investigate the effect of the drying speed and reactant composition on the structure and composition of the resulting particles and relate that to the release kinetics of the active ingredient. In addition, we will crystallize the amorphous composite particles and investigate the influence of the structure on the distribution of the actives within the matrix and its permeability. This project is done in collaboration with Firmenich who has all the infrastructure to quantify the release kinetics of volatile active ingredients.

EPFL2022

2013

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Testing chemicals for fish acute toxicity is a legal requirement in many countries as part of environmental risk assessment. To reduce the number of fish used, substantial efforts have been focused on alternative approaches. Prominently, the cell viability assay with the rainbow trout (Oncorhynchus mykiss) gill cell line, RTgill-W1, has proven to be highly predictive and robust. Like the gills, the intestine is considered a major site of chemical uptake and biotransformation, but, in contrast to the gills, it is expected to be exposed to more hydrophobic chemicals, which enter the fish via food. In the present study, we therefore aimed to extend the cell bioassay to the rainbow trout epithelial cell line from intestine, RTgutGC. Using 16 hydrophobic and volatile chemicals from the fragrance palette, we show that also the RTgutGC cell line can be used to predict fish acute toxicity of chemicals and yields intra-laboratory variability in line with other bioassays. By comparing the RTgutGC toxicity to a study employing the RTgill-W1 assay on the same group of chemicals, a fragrance-specific relationship was established that reflects an almost perfect 1:1 relationship between in vitro and in vivo toxicity results. Thus, both cell lines can be used to predict fish acute toxicity, either by extrapolating based on the in vivo-in vitro relationship or by taking the in vitro results at face value. We moreover demonstrate the derivation of non-toxic concentrations for downstream applications that rely on a healthy cell state, such as the assessment of biotransformation or chemical transfer.

SPEKTRUM AKADEMISCHER VERLAG-SPRINGER-VERLAG GMBH2020