Tris contains a primary amine and have a pKa value of 8.07 at 25 °C, which implies that the buffer has an effective pH range between 7.07 and 9.07.

But Bis-tris buffer have a tertiary amine with labile protons having a pKa of 6.46 at 25°C. It is an effective buffer between the pH 5.8 and 7.3.

Hi Joseph Anyanwu, answer below may help you:

BIS-TRIS (C8H19NO5; Molecular Weight 209.24; pH 5.8 and 7.3)

BIS - TRIS is the common name for bis(2-hydroxyethyl)amino-tris(hydroxymethyl)methane, a water -soluble, tertiary amine compound containing five hydroxyl (–OH) groups.

Synonyms: 2,2-Bis(hydroxymethyl)-2,2',2"-nitrilotriethanol, or 2-Bis(2-hydroxyethyl)amino-2-(hydroxymethyl)-1,3-propanediol.

Use: When added to aqueous solutions, BIS-TRIS maintains a steady pH in the 5.8 to 7.3 range and is used as a buffer in the life sciences industry for biochemical research (for example, cell cultures, gel electrophoresis and more).

TRIS (C4H11NO3; Molecular Weight 121.14; pH 7.0 and 9.2).

It is tris(hydroxymethyl)aminomethane. Water -soluble. It contains a primary amine and thus undergoes the reactions associated with typical amines, e.g. condensations with aldehydes.

Synonym: 2-Amino-2-(hydroxymethyl)-1,3-propanediol, THAM, Tris base, Trometamol

Use: Tris buffer is used in many applications within biochemistry and molecular biology laboratories and is a component in TAE and TBE (electrophoresis running buffer). Tris has a slightly alkaline buffering capacity between pH 7.0 and 9.2, which coincides with the typical physiological pH of most living organisms. Tris buffer is a good option for washing procedures in cell cultures and is suitable as suspension buffer for biological samples. Tris is also used as a primary standard to standardize acid solutions for chemical analysis; to increase membrane permeability of cell membranes; as alternative to sodium bicarbonate in the treatment of metabolic acidosis.

Thank you all for your response