D(-)-N-Methylglucamine buffer for pH 8.5 to 10.5.

A new amine buffer for the pH range 8.5 to 10.5 based on D(-)-N-methylglucamine and its hydrochloride is described. Important physical and chemical constants characterizing this buffer system have been determined: thermodynamic pKa = 9.52 (25 degrees C), buffer capacity = 0.055, dilution value pH 1/2 = -0.02, temperature coefficient dpKa/dT = 0.023, the heat of ionization delta H degrees = 36.93 kj mol-1. D(-)-N-Methylglucamine, which is available in highly purified form, is highly soluble in water. Thus one can prepare either buffer solutions or stable solid mixtures when combined with D(-)-N-methylglucaminium chloride. D(-)-N-Methylglucamine buffers are suitable for both biochemistry and pH control.