Lipophilicity range

A clear trend was also apparent among the physicochemical properties, since the lipophilicity range yielded the best correlations for both ApKj b and ApKj, while the dipole space yielded the lowest. Interestingly, all significant correlation coefficients were posihve, implying that tti-AR selectivities are mainly proportional to variations in physicochemical properties, as expressed mainly by range. 

To speed up the lipophilicity determination it was also proposed to use gradient elution procedures (for a review and guidelines, see references [5,101]). This generic approach is particularly useful when series of compounds with a broad lipophilicity range have to be tested since both polar and non-polar solutes can be retained with a reasonable elution time. 

Offline precolumn derivatization is the most common alternative in this respect it involves separating the esters obtained from the organic acids by reversed-phase chromatography, which amply surpasses solvophobic chromatography (i.e., the use of undissociated acids as such) and allows gradient elution techniques to be applied, thanks to the wider lipophilicity range covered by the derivatized compounds. 

Forty years later Meyer [1], and at the same time Overton [2], observed a linear relationship between the activity of narcotics and their oil-water partition coefficient. An 40 years after that, a thermodynamic interpretation of this relationship was provided by Ferguson [3], which also explained cut-off of biological activity that is sometimes observed after a certain lipophilicity range has been passed. 

Lombardo et al. use also different octanol concentration in their isocratic method. They use an LC-ABZ column (Pagliara). This method is capable to cover a wide lipophilicity range with good correlation with log Pow-... 

At room temperature, ca 60 wt % ethylene oxide is needed to solubilize the fatty acids. Surface activity of the ethoxylates is moderate and less than that of alcohol or alkylphenol ethoxylates (84). The ethoxylates are low foamers, a useful property in certain appHcations. Emulsification is the most important function. Its importance is reflected in the wide range of lipophilic solubiHties available in the commercial products. Like all organic esters, fatty acid ethoxylates are susceptible to acid and alkaline hydrolysis. 

Sorbitan oleate and the monolaurate are pale yeUow Hquids. Palmitates and stearates are light tan soHds. Sorbitan esters are not soluble in water but dissolve in a wide range of mineral and vegetable oils. They are lipophilic emulsifiers, solubiHzers, softeners, and fiber lubricants that find appHcation in synthetic fiber manufacture, textile processing, and cosmetic products. Sorbitan esters have been approved for human ingestion and are widely used as emulsifiers and solubiHzers in foods, beverages, and pharmaceuticals. 

Lindane is one of eight different hexachlorocyclohexane (HCH), C H Cl, isomers and its Chemical Abstract n.2cniQ is la, 2a 3P, 4a, 5a 6P-hexachlorocyclohexane [58-89-9] (y-HCH or y-BHC, ben2ene hexachloride) (80). Commercial products containing lindane are marketed as either a mixture of isomers or as the pure y-BHC isomer. Not unexpectedly, lindane is a highly stable lipophilic compound and it has been used extensively worldwide as an insecticide. In contrast, hexachloropentadiene, C Cl, is an extremely reactive industrial intermediate used as a chemical intermediate in the synthesis of a broad range of cyclodiene-derived pesticides, which include endosulfan, endrin, heptachlor, and several different organohalogen flame retardants (81). 

These characteristics are typically classified as a hydrophile-lipophile balance (HLB value). For example, hydrophilicity may be denoted within a range of 2 to 20, with true solutions being obtained at HLB values >14 and poor dispersibility occurring at HLB values <6. Oil-in-water emulsification requires a high HLB value surfactant, while water-in-oil emulsification needs a low HLB value surfactant. 

The following ranges of half-lives have been reported for vertebrate species, which are presumably related to rates of biotransformation as the original lipophilic compounds show little tendency to be excreted unchanged. 

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