What is the ionic strength of Tris and other biological buffers

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Different buffers have different ionic strengths. In the biochemical detection system, the ionic strength may also have a serious impact. Low ionic strength buffers include Tris, Bis-Tris, Tricine, etc., high ionic strengths include HEPES, PIPES, etc., and phosphate buffers have higher ionic strength, so many biological experiments are replaced by Tris.


Tris biological buffer raw materials


Interpretation of buffer ionic strength

Ionic strength is a measure of the concentration of ions in a solution. It is a function of the concentration of all ions in the solution. It is defined as follows: Ionic strength I is equal to the molar concentration of each ion i in the solution (mi) multiplied by the valence of the ion The sum of the terms obtained by squaring (zi) is half.Among them: c is the mass molar concentration of the ion (unit mol/kg), is the number of charges carried by the ion, such as 2 for magnesium ion.


Ionic strength of buffer

When the concentration is the same, for strong electrolytes, the ions with high valence have more charges and higher ionic strength, for example, magnesium ions are larger than sodium ions. However, buffers such as Tris and Bicine are usually weak electrolytes (the sodium hydroxide added is a strong electrolyte), and the ionic strength generally depends on the degree of ionization.


Buffer ionic strength and salt effect

There are correlations and differences between the ionic strength of the buffer and the salt effect, and some people may be confused. Electrolyte concentration and ionic strength affect the solubility of other salts. Salt effect refers to the mutual influence between different electrolytes, which will affect the dissociation degree and ionic strength. The solubility of the insoluble electrolyte solution increases after the strong electrolyte is added, which is also called the salt effect, and the ionic strength increases. The neutral salt effect and the same ion effect (much greater than the salt effect) will also change the ionic strength of the system. In addition, an increase in ionic strength usually causes an increase in osmotic pressure. These are all different concepts. Pay attention to the distinction. You can learn more about them.


It should be noted that a buffer with a low ionic strength is not necessarily better. For example, Tris has a lower ionic strength than HEPES, but HEPES is usually used in cell culture and the price is higher. Desheng is a buffer manufacturer and can provide a variety of biological buffers suitable for different experiments.