This Recommendation provides requirements for defining, testing and verifying the performance of spectrophotometers used in clinical chemistry laboratories to determine concentrations of analytes in samples of blood, serum, plasma, liquor cerebrospinalis, urine, etc. derived from the human body by measuring the characteristic partial internal absorbances of prepared solutions in optical cells (cuvettes). The major components specified in this Recommendation reflect the current technology and are not intended to preclude new developments. The following are beyond the scope of this Recommendation and are therefore not covered by it: • Influences on the accuracy of measurement by automated preparation and automated supply of samples; • Sampling plans, sample preparations and measurement procedures for specific clinical analytes; • Spectrophotometers at the development stage; • Spectrophotometers in bedside monitoring systems and in self-checking monitoring systems; and • Reflection spectrometers and atomic absorption spectrometers.