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If different species occur in the octanol-water system by dissociation or association, several P-values and one D-value exist for the system. If, on the other hand, the substance is only present in a single species, the P and D values are identical. P is usually expressed as a common logarithm, i.e. Log P (also Log P ow or, less frequently, Log ...
A faster method of log P determination makes use of high-performance liquid chromatography. The log P of a solute can be determined by correlating its retention time with similar compounds with known log P values. [40] An advantage of this method is that it is fast (5–20 minutes per sample).
Chemicals with high BCF values are more lipophilic, and at equilibrium organisms will have greater concentrations of chemical than other phases in the system. Body burden is the total amount of chemical in the body of an organism, [ 12 ] and body burdens will be greater when dealing with a lipophilic chemical.
OPEs exhibit a wide range of octanol/water partition coefficients where log Kow values range from -0.98 up to 10.6. [5] Mono- and di- esters are usually water soluble, particularity biomolecules. Tri-esters such as flame retardants and plasticisers have positive log Kow values ranging between 1.44 and 9.49, signifying hydrophobicity.
The octanol-water partition coefficient, usually expressed as its logarithm (Log P), is a measure of differential solubility of a compound in a hydrophobic solvent and a hydrophilic solvent (water). The logarithm of these two values enables compounds to be ranked in terms of hydrophilicity (or hydrophobicity).
where log denotes a logarithm to base 10 or common logarithm, and K diss is a stepwise acid dissociation constant. For bases, the base association constant , p K b is used. For any given acid or base the two constants are related by p K a + p K b = p K w , so p K a can always be used in calculations.
A random variable which is log-normally distributed takes only positive real values. It is a convenient and useful model for measurements in exact and engineering sciences, as well as medicine, economics and other topics (e.g., energies, concentrations, lengths, prices of financial instruments, and other metrics).
Any compound with a log Kow of less than or equal to 3 can concentrate in a POCIS sampler. [5] Applicable classes of contaminants measured by POCIS are pharmaceuticals, household and industrial products, hormones, herbicides, and polar pesticides (Table 1).