White Paper: Advances in UV/Vis Spectroscopy – Stray Light and Performance Verification

Stray light is one of the most important factors influencing the photometric performance of UV/Vis spectrophotometers. Understanding the impact of stray light on measurement accuracy, precision and repeatability is crucial in quality control applications, where these instruments must always perform according to their design specifications.

Stray light significantly affects UV/Vis measurements. This issue, and the procedure for stray light testing, has been widely discussed since the US Pharmacopeia first included a chapter on UV/Vis spectroscopy, and is of great interest to quality control applications in the clinical, pharmaceutical and industrial sectors. In all these fields, and especially for laboratories working according to Pharmacopeia regulations, it is important that the UV/Vis spectrophotometer performance is monitored and documented on a regular basis.

This white paper explains the origins and accurate measurement of stray light, comparing the US Pharmacopeia’s current and previous methods for measuring stray light, and describing the advantages of the latest protocol. It also discusses the automatic measurement of other important performance verification tests for UV/Vis instruments. Topics include:

  • The optical performance of a UV/Vis spectrophotometer
  • Performance verification tests to assess measurement quality
  • What is stray light?
  • How is stray light measured?
  • Specific Wavelength Method (SWM)
  • Solution Filter Ratio Method (SFRM; Melienz)
  • Assessment of the SWM and SFRM methods
  • Correlation between the SWM and SFRM stray light values
  • Materials for stray light tests in different wavelength ranges
  • Automatic determination of optical performance parameters, including stray light