Use of Tris buffers for quality control of blood pH

Tris(hydroxymethyl)aminomethane buffers have been established as sensitive and convenient indicators of the reliability of blood pH analysis. These buffers were compatible for routine use with blood pH equipment from major manufacturers, except for 2 instruments. A 7 mth study demonstrated the necessity of a routine quality control program, as well as the need for systematic cleaning and maintenance of pH equipment. Tris(hydroxymethyl)aminomethane buffers were not suitable as primary standards because the stated values with commercial pH equipment that had been standardized with phosphate buffers from the National Bureau of Standards could not be obtained. The relative standard deviation for measurement of hydrogen ion activity, 4.1%, indicates a need for improvement in the design and operation of equipment for the measurement of blood pH.