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The distribution constant (or partition ratio) (K D) is the equilibrium constant for the distribution of an analyte in two immiscible solvents. [1] [2] [3]In chromatography, for a particular solvent, it is equal to the ratio of its molar concentration in the stationary phase to its molar concentration in the mobile phase, also approximating the ratio of the solubility of the solvent in each phase.
However, since water is in vast excess, the concentration of water is usually assumed to be constant and is omitted from equilibrium constant expressions. Often, the metal and the ligand are in competition for protons. [note 4] For the equilibrium p M + q L + r H ⇌ M p L q H r. a stability constant can be defined as follows: [28] [29]
[10]: 280–4 Hence, a single experiment can be used to measure the logarithms of the partition coefficient (log P) giving the distribution of molecules that are primarily neutral in charge, as well as the distribution coefficient (log D) of all forms of the molecule over a pH range, e.g., between 2 and 12.
Ion chromatography (or ion-exchange chromatography) is a form of chromatography that separates ions and ionizable polar molecules based on their affinity to the ion exchanger. [1] It works on almost any kind of charged molecule —including small inorganic anions, [ 2 ] large proteins , [ 3 ] small nucleotides , [ 4 ] and amino acids .
Partition equilibrium chromatography is a type of chromatography that is typically used in gas chromatography (GC) and high performance liquid chromatography (HPLC). The stationary phase in GC is a high boiling liquid bonded to solid surface and the mobile phase is a gas. [ 4 ]
The value of the equilibrium constant for the formation of a 1:1 complex, such as a host-guest species, may be calculated with a dedicated spreadsheet application, Bindfit: [4] In this case step 2 can be performed with a non-iterative procedure and the pre-programmed routine Solver can be used for step 3.
Biotin and avidin bind with a dissociation constant of roughly 10 −15 M = 1 fM = 0.000001 nM. [7] Ribonuclease inhibitor proteins may also bind to ribonuclease with a similar 10 −15 M affinity. [8] The dissociation constant for a particular ligand–protein interaction can change with solution conditions (e.g., temperature, pH and
The CRFs in thin layer chromatography characterize the equal-spreading of the spots. The ideal case, when the RF of the spots are uniformly distributed in <0,1> range (for example 0.25,0.5 and 0.75 for three solutes) should be characterized as the best situation possible.