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The isoelectric point (pI, pH(I), IEP), is the pH at which a molecule carries no net electrical charge or is electrically neutral in the statistical mean. The standard nomenclature to represent the isoelectric point is pH(I). [1] However, pI is also used. [2] For brevity, this article uses pI.
The equation for determining the isoelectric point is as follows: p I = p K a + p K b 2 {\displaystyle pI={{pKa}+{pKb} \over 2}} In the papermaking process, the pigment dispersions are generally kept at a pH above 8.0.
Whereas the isoionic point is at net charge zero in a deionized solution. Thus, the isoelectric and isoionic points are equal when the concentration of charged species is zero. For a diprotic acid, the hydrogen ion concentration can be found at the isoionic point using the following equation [2]
The isoelectric point (pI) is the pH of a solution at which the net primary charge of a protein becomes zero. At a solution pH that is above the pI the surface of the protein is predominantly negatively charged and therefore like-charged molecules will exhibit repulsive forces.
The isoelectric point of casein is 4.6. Since milk's pH is 6.6, casein has a negative charge in milk. The purified protein is water-insoluble. While it is also insoluble in neutral salt solutions, it is readily dispersible in dilute alkalis and in salt solutions such as aqueous sodium oxalate and sodium acetate.
The iso-electric point is the pH value at which the zeta potential is approximately zero. At a pH near the iso-electric point (± 2 pH units), colloids are usually unstable; the particles tend to coagulate or flocculate. Such titrations use acids or bases as titration reagents. Tables of iso-electric points for different materials are available ...
The pzc is the same as the isoelectric point (iep) if there is no adsorption of other ions than the potential determining H + /OH − at the surface [clarification needed]. [8] This is often the case for pure ("pristine surface") oxides in suspension in water. In the presence of specific adsorption, pzc and isoelectric point generally have ...
Isoelectric may refer to: Isoelectric point, the pH at which a particular molecule carries no net electrical charge; Isoelectric focusing, a technique for separating different molecules by differences in their isoelectric point; Isoelectric line representing the absence of electrical activity on an electrocardiogram