Physico chemical properties and processing possibilities of
From there, the chemical can reach tissues in living systems and interact with cellular macromolecules.
It is seen that different fresh macapuno endosperms do not significantly differ from each other in sensory attributes except for juiciness and texture. When measured data are unavailable, the DfE will consider the octanol-water Kow and octanol-air Koa partition coefficients.
Use of Physicochemical Properties to Predict Aquatic Bioavailability and Toxicity Bioavailability is a measure of the amount of a chemical and the rate at which it crosses a barrier of the external environment and enters an organism's circulation. In cases where measurement is not feasible or is prohibited by cost, estimated parameters can be determined through a variety of methods, as discussed in the next section.
What are physicochemical properties
Accurate estimation of these attributes based on chemical structure necessitates prior optimization of the geometry via a conformational analysis and energy optimization. Semi-empirical methods can be accurate and are notably faster than ab initio or DFT methods; however, their performance is tied to the training set used in their development. Measured values of these properties often can be obtained from the scientific literature Leo Table shows the characterization and ranges that define classification scores for logP for three frameworks. Solvation properties of interest in alternatives assessment can be divided into three main types: a phase partitioning, b solubility, and c colligative properties: Phase partitioning. Rather than attempting to provide a detailed description of these properties and their relation to biological activity, instead we illustrate the potential utility of one such property to alternatives assessment. Chemicals with the propensity to environmentally partition into sediments will be more likely to sorb onto soils, so the soil-water phase partition coefficient Kd will be informative for both systems. The DfE evaluates the ability of a chemical to bioaccumulate. Physico-chemical properties and processing possibilities of macapuno cultivars developed at Leyte State University [Baybay, Leyte, Philippines] Lauzon, R. Large chemical structural databases combined with recent developments in quantitative structure property relationships have greatly expanded the potential for rapid assessment of chemicals Howard and Muir This is true for chemicals with slow excretion or metabolism rates, during which time dilution by growth generally occurs. This can be a major difference from the degradation of smaller molecules. The most prominent properties that have been shown to impact chemical toxicokinetics include: 1.
A multitude of electronic properties and molecular attributes have been used to describe biological activity of chemicals. The modes of degradation depend on the environmental compartment and conditions pH, UV irradiation, microorganism population, etc.
Ver texto completo. As will be discussed in a later section, these coefficients provide insight into environmental partitioning of the molecule and the potential for bioaccumulation.
Physicochemical properties slideshare
Regardless of cultivar, macapuno has acceptable sensory qualities. Some more fundamental approaches use semiempirical and higher level quantum calculations; however, these are problematic for larger systems, since they require calculating very small differences in the energy of relatively large molecules Shields and Seybold, …. As important as these data are, obtaining them is relatively fast and inexpensive, and can be readily done at the initial stages of the alternatives assessment. Scheme illustrating the relationships between the three primary types of physicochemical properties assessed in the committee's framework and their relationship to environmental fate, biological and ecological processes, and toxicity. For a chemical to exert a toxic effect, it typically must be bioavailable at a level that allows the chemical or its metabolite to reach a biochemical target, where it can exert its toxicologic effect. Box provides a brief description of the elements of the committee's suggested approach. Sorption reactions are reversible and highly dependent on pH, with higher rates of sorption occurring at higher pH, increasing bioavailability as pH decreases i. However, given that standard protocols have been developed to provide guidance for conducting BAF tests to enable comparability among chemicals, these data should be given preference over BCF values for estimating bioaccumulation potential in hazard classification and ranking. The committee cautions that given the active research in the field and the potential for special case concerns to arise for a given compound e. Thus, the quantum method and the basis set 16 used impact the dipole moment and polarizability calculations. For more information about the application of physicochemical data to ecotoxicology, see Chapter 7. These categories are explained in more detail in Table The solubility equation developed by Yalkowsky can be used to estimate intrinsic water solubility at 25oC logS for structurally diverse organic substances Ran and Yalkowsky Colligative properties.
At Pacific BioLabs, water content is determined using the Karl Fischer titration method — an industry standard. A number of different software packages and algorithms are available for predicting physicochemical properties, and predictions are often in excellent agreement with experimentally-derived values.
Some more fundamental approaches use semiempirical and higher level quantum calculations; however, these are problematic for larger systems, since they require calculating very small differences in the energy of relatively large molecules Shields and Seybold, ….
Questions remain about whether aquatic BCF and BAF values are predictive for terrestrial organisms, where uptake into the food chain begins with movement of chemicals from soils into plants.
based on 103 review