Physico-chemical properties INDEX

Several kinds of detection systems have been applied to CE [1,2,43]. Based on their specificity, they can be divided into bulk property and specific property detectors [43]. Bulk-property detectors measure the difference in a physical property of a solute relative to the background. Examples of such detectors are conductivity, refractive index, indirect methods, etc. The specific-property detectors measure a physico-chemical property, which is inherent to the solutes, e.g. UV absorption, fluorescence emission, mass spectrum, electrochemical, etc. These detectors usually minimize background signals, have wider linear ranges and are more sensitive. In Table 17.3, a general overview is given of the detection methods that are employed in CE with their detection limits (absolute and relative). 

Wang, Y.H., Wong, P.K. (2003) Correlation relationships between physico-chemical properties and gas chromatographic retention index of polychlorinated-dibenzofurans. Chemosphere 50, 499-505. 

In India, small seeds generally had higher oil content than larger seeds and the main characteristics were specific gravity (15°C), 0.9304 refractive index (15°C), 1.4795 optical rotation, +35° saponification value, 181.2 iodine value (Wijs), 99 unsaponified material, 3.7%. The expressed oil is classified as semi-drying and is a source of lauric and adipic acids (Weiss, 2002). Table 12.4 gives the average physico-chemical properties of fennel volatile oil. 

The failure of drugs at later stages of development, particularly in clinical trials, is very expensive for drug developers and, more importantly, patients. To better understand the key reasons for these failures, Lipinski et al,14 undertook an analysis of the properties of compounds that entered Phase II human clinical trials. They selected a subset of 2245 compounds from the World Drug Index (WDI) database of over 50000 compounds after eliminating the majority of compounds for various well-reasoned criteria. This subset of compounds had assigned trade names and, as a result, were assumed to have entered Phase II oral efficacy studies and be expected to have superior physico-chemical properties since they would have passed most of the other earlier clinical trial hurdles. 

The logarithm of this index was used to model different -> physico-chemical properties [Cash, 1995c], showing that it can suffer from the drawback that the determinant values are often equal to zero. 

The Diverse Property-Derived method (DPD method) is based on the partitioning of six noncorrelated molecular descriptors and physico-chemical properties [Ashton, Jaye et al, 1996]. These are a lipophilicity descriptor (CLOGP), an electrotopological index calculated as normalized sum of the squares of the atomic electrotopological state indices, the number of hydrogen-bond acceptors (HBA), the number of hydrogen-bond donors (HBD), a flexibility index defined as the ratio of the —> Kier shape descriptors over k, and the aromatic density defined as the number of aromatic rings over the molecular volume (Table Cl). 

Herdan, J., Balaban, A.T, Stoica, G., Simon, Z., Mracec, M. and Niculescuduvaz, 1. (1991) Compounds with potential cancer preventing activity. 1. Synthesis, physico-chemical properties and quantum chemical indexes of some phenolic and aminophenolic antioxidants. Rev. Roum. Chim., 36, 1147—1160. 

Chemical compounds are ubiquitous in the environment. Some are dispersed on purpose and some are released accidentally. Some have local effects while others have a global impact. This impact has been variously quantified (see Helm 2003 and chapter by Helm, p. 285 Bruggemann and Drescher-Kaden 2003 Halfon and Bruggemann 1989 Bruggemann and Munzer 1993). For example physico-chemical properties and environmental persistence, i.e. criteria, have been combined in an index function... 

Notes-. Physico-chemical properties of the two most common iodate salts. The Merck Index, (1996) CRC Handbook of Chemistry and Physics, (1993). Note the differing ratio of iodine in the salts. Both salts are highly soluble - a prerequisite for substances to be applied by spraying in aqueous solution to salt. 

Of all the physico-chemical properties, it is the rheology which shows the strongest temperature dependence. For instance, the decrease in apparent viscosity at a fixed shear rate is well represented by the Arrhenius-type exponential expression the pre-exponential factor and the activation energy are then both fimctions of shear rate. It is thus customary to denote the temperature dependence using rheological constants such as the power-law consistency coefficient and flow behaviour index. It is now reasonably well established that the flow behaviour index, n, of suspensions, polymer melts and solutions is nearly independent of temperature, at least over a range of 40-50°C, whereas the consistency coefficient exhibits an exponential dependence on temperature, i.e. 

Under the assumption that physico-chemical properties are constant and specifications result in an index 1 model, the algebraic equations are always substitutable into (I). 

Many attempts have been made to correlate the enantioselective properties of enzymes with structure and/or process conditions [61, 70-73]. Attempts to correlate the effect of a particular medium on the enantioselectivity of an enzyme-catalyzed reaction with physico-chemical descriptors of the solvent have also been reported by a number of groups [22, 59, 64, 74]. Correlations with solvent size [75], dielectric constant [59], polarizability, electron pair acceptance index [76], logP [17],... 

IlMei et al. (39) derived the VHSE5 composite index of electronic effects. This scale (Vectors of Hydrophobic, Steric, and Electronic properties) was derived from principal components analysis of 50 different physico-chemical variables. 

Martorell, C. Calpena, A.C. Escribano, E. Poblet, J.M. Freixas, J. Influence of the chromatographic capacity factor (log L) as an index of lipophilicity in the antibacterial activity of a series of 6-fluoroquinolones. Relationship between physico-chemical and structural properties and their hydrophobicity. J. Chromatogr., A 1993, 655, 177-184. 

The dectrotopological state index (Si) is an extension of the purely topological index [55]. Electronic properties (i.e., the charge distribution in the molecule) are also considered. Atoms with identical T may differ in their Si. Electrotopological state indices have been used successfully to predict physico-chemical data, such as basicity (pJCa) or Hpophilicity (logP), as well as for quantitative structure-activity relationship (QSAR) or QSPR studies. 

One of the most comprehensive resources of amino acid properties freely available on line is the amino acid index database (AAindex), which includes numerical indices representing various physico-chemical, biochemical, and statistical properties of amino acids and pairs of amino acids. AAindex database has been made publicly available by the Japanese GenomeNet database service (http //www.genome.jp/aaindex/). 

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