UV/VIS SPECTROPHOTOMETRY

The ultraviolet-visible (UV-VIS) absorption spectrophotometer represents a category of analytical instrumentation in many laboratories of nearly every sector of the scientific workplace. A workhorse for quality control (QC) analysis, the UV-VIS spectrophotometer is indispensable in FDA-regulated laboratories around the world for the analysis and characterization of proteins, DNA and much more.

Spectrophotometric Metrology is the science behind analytical instrument qualification (AIQ) for spectrophotometers in FDA-regulated healthcare testing laboratories. It is essential for ensuring confidence in analytical UV/VIS measurement results. The “calibrated” or “qualified” status of a spectrophotometer can be easily challenged when UV/VIS metrology is ignored or trivialized in the qualification process (check out Auditor Primer), and the integrity of the laboratory spectrophotometer measurement results may be jeopardized leading to inappropriate actions or decisions.

The qualification of an analytical UV/VIS absorption spectrophotometer is focused on the following four (4) instrumental parameters:

  • Spectral Resolution
  • Wavelength Scale Accuracy
  • Stray Radiant Energy (Stray Light)
  • Photometric Scale Accuracy and Linearity

Spectrophotometer qualification tests typically require artifact reference materials that are comprised of filters certified for a specific optical parameter such as transmittance (or absorbance) or wavelength. The artifact reference materials are issued either as chemical solutions or solid optical filters. The chemical solutions are sealed in glass ampoules or fused-silica quartz cuvettes.

Chemical solutions sealed in glass ampoules are termed consumable and are intended to be used only at the time the solution is withdrawn from the ampoule. Spectrophotometric measurement standards fabricated from solid optical materials or chemical solutions sealed in cuvettes can be used repeatedly over time. However, it is necessary to periodically update their certifications to ensure that the reference values and their uncertainties are scientifically valid at the time of their use.

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