UV-Vis Spectrophotometry

Ultraviolet-Visible Light Spectrophotometry

and its Capabilities

  • Commonly called UV-Vis Spectroscopy or ultraviolet-visible light spectroscopy
  • Determines the absorption of ultraviolet and visible light in solutions in transmission mode
  • Used to measure the concentration of colored or UV-absorbing ingredients in solution
  • A chemical may be added to the solution that creates a chromofore when that molecule reacts with the chemical or ion that one wishes to detect and whose concentration is to be measured, allowing the detection and concentration measurement of species which do not absorb light otherwise
  • Absorbance is governed by the Beer-Lambert Law
  • Quantification is achieved by comparing the spectrum of the unknown concentration to spectra for known, prepared concentrations of the species of interest
  • In cases in which the species producing the absorbance is not known, it may have to discovered by other means
  • Absorbance spectra lend themselves to quality control testing

UV-Vis Spectroscopy System

  • Ocean Optics Inc. FLAME-CHEM-UV-VIS
  • 200 – 850 nm wavelength
  • SONY ILX511B linear silicon CCD array detector
  • 25 µm entrance slit
  • 1.5 nm (FWHM) optical resolution
  • 250:1 signal-to-noise ratio
  • 1300:1 dynamic range for a single acquisition
  • 1 ms to 65 s integration time
  • <0.10% stray light at 435 nm
  • Deuterium UV light source
  • Tungsten halogen visible light source
  • 1 cm standard path-length cuvettes
  • Can use optical filters

Applications

  • Measuring lead, copper, iron, cadmium, mercury, and other metal ion concentrations in water
  • Detecting the change in antifreeze or windshield washing fluid compositions due to use or the passage of time
  • Quality control of beverages such as sodas, wines, beers, whiskies, and liqueurs
  • Characterizing the change in motor oils with use
  • Detecting soluble surface contamination removed from a surface by a solvent
  • Characterizing a solution causing corrosion and changes in its composition during an electrochemical corrosion experiment
  • Detecting and measuring organic contaminants in a solvent
  • Measuring the transmission of a liquid at a particular wavelength between 200 and 850 nm