Buffers in the Range of pH 6.5 to 9.6. ∗

Abstract

In the pH range between 6.5 and 9.6, the buffers generally used have been phosphate, barbital, 1 ammonium salts and carbonate. 2 Among these, phosphate and carbonate are incompatible with Ca salts; ammonium salt buffers are not entirely stable; barbital, on account of its low solubility, can be prepared in low concentrations only and, in addition, inhibits certain enzyme systems. 3 Mertz and Owen 4 have suggested the use of imidazole as a buffer in the physiologic pH range, compatible with Ca; however, its high cost is almost prohibitive.

Three new buffers: 2,4,6-collidine, tris(hydroxymethyl)-aminomethane and 2-amino-2-methyl-1,3-propanediol, are suggested for the use in the pH range between 6.5 and 9.6. They are quite soluble, do not precipitate Ca salts, and are low in price. They were found to be stable at room temperature for a period of over 3 months. Collidine and Tris (hydroxymethyl)-aminomethane, to be used in the pH ranges between 6.5 and 8.3, andb between 7.2 and 9.0, respectively, were tested by Dr. E. S. Guzman Barron for their effect on the O2 uptake of rat kidney slices in the presence of 0.01 M pyruvate. The concentration of the buffers was 0.02 M, phosphate buffer being used as a control. The results with the different buffers were all well within the limits of experimental error, thus showing complete lack of inhibitory action. Tris(hydroxymethyl)-aminomethane and 2-amino-2-methyl-1,3-propanediol (range, pH 8.0 to 9.7) were tested for their effect on alkaline phosphatase at pH 9.1, 0.005 M glycerophosphate being used as a substrate. Barbital and Delory and King's 2 carbonate buffers served as controls. Again, no inhibitory effect was was noted.

The pK, values of the new buffer stances were determined by the determination of the pH of their tralized 0.05 M solutions at 23°C and The apparatus used was a Leeds and potentiometer with glass and calomel trodes. Phthalate buffer served as a standard.