Role of reference materials for the realization of physicochemical properties. Past, present, and future

Reference materials have long been considered essential for both calibration and checking the correct operation of equipment used for the determination of physicochemical properties. Up until the 1970s, the maintenance of pure reference materials and the means to verify their properties through measurement using state-of-the-art equipment was the prerogative of many national standards laboratories. Over the last 30 years, many of the standards laboratories have either limited or eliminated their activity in maintaining both reference materials and state-of-the-art measuring equipment. One reason is the ready availability of high-purity materials from commercial sources and the ease with which one can now determine purity. A second reason is the ready availability of instruments to measure digitally fundamental quantities such as time, temperature, length, frequency, and voltage accurately has enabled chemical calibration using reference materials to be replaced in many instruments by electrical calibration. At the same time, digitization has enabled the computerization of the whole measurement process. Such automated devices, if not checked with reference materials, can give highly reproducible results but have large systematic errors, leading to poor values. The role of physicochemical reference materials in the past and the present will be outlined, and their status in the future will be explored.