Use of Tris Buffers for Quality Control of Blood pH

Abstract 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 two instruments. A seven-month 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 found not to be suitable as primary standards because we could not obtain the stated values with commercial pH equipment that had been standardized with phosphate buffers from the National Bureau of Standards. 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.