Accuracy and linearity of spectrophotometers

SUMMARY Solutions of cobalt nitrate sealed in vials were circulated to all clinical chemistry labora-tories in the United Kingdom. Participants reported wavelengths of maximum absorbance together with the actual absorbances obtained. The results were compared with values obtained from the National Physical Laboratory. The results show a wide scatter, and several instruments were extensively repaired or replaced as a result of the survey. The most recently marketed machines had the best performance, and it is suggested that regular quality control and maintenance of the machines is vital. It is intended to set up a scheme for regular monitoring of spectrophotometer performance. The balance and the spectrophotometer are the two basic pieces of equipment available to the chemical analyst. It is essential for accurate and precise analytical work that both are adequately main-tained and subject to quality control procedures. In 1977 the Quality Control Working Party (QCWP) tested the feasibility of studying the per