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• Spectroscopy


  The study of radiated energy and matter to determine their interaction
• Electromagnetic spectrum


  Includes ultraviolet (UV), visible, infrared (IR), radio, cosmic, and X rays
• As wavelength gets shorter

  The electromagnetic radiation increases
• Electromagnetic radiation


  A form of radiant energy released by electromagnetic processes such as visible light or invisible forms such as radio waves and x-rays
• Electromagnetic radiation


  • Exhibits a wide and specific range of wavelength, where its Energy is inversely proportional to its wavelength (distance between successive crests of a wave)
  • Exhibits a direction of propagation and wave-like properties (oscillations)
• Spectroscopic methods


  • Ultra-violet visible (UV-Vis) adsorption spectroscopy
  • Infrared (IR) absorption spectroscopy
  • Nuclear Magnetic Resonance (NMR) spectroscopy
• Photon


  A tiny particle of light or electromagnetic radiation
• Terms


  • Frequency - number of times electric field radiation oscillates in one second (Hertz)
  • Wavelength - distance between successive waves (nanometer)
  • Amplitude - is the max. distance extends its middle position
• Spectrometry


  The application of spectroscopy which deals with the measurement of spectra
• Spectrophotometry


  A branch of spectrometry which deals the measurement of the absorption of electromagnetic radiation
• Chromophore


  A particle or molecule that can absorb light and resulting in a UV-visible spectrum
• Chromophores


  • Exhibit absorption spectra and absorb light in the visible and ultraviolet range
• Lambert's Law


  The power of a transmitted radiant beam decreases as the thickness of the solution containing the absorbing chemical species increases
• Beer's Law


  The power of a transmitted radiant beam decreases as the concentration of the solution containing the absorbing chemical species increases
• Beer-Lambert's Law


  The power of a transmitted radiant beam decreases as the thickness and concentration of the solution containing the absorbing chemical species increases
• Electronic energy (Ee) transitions


  The promotion of electrons in sigma, pi and n orbitals
• Types of electrons


  • n electron - not involved in bonding (nonbonding) - molecules containing O,S, N or halogens
  • Sigma & pi electron - bonding
  • Sigma * & pi * - antibonding
• Spectrophotometer


  An instrument which has a radiant energy dispersing device such as prism or grating and the associated electronics which permit the measurement of wavelength and radiant power
• Components of a spectrophotometer

  • Light sources - a deuterium for the UV region and a quartz halogen or tungsten lamp for the visible region
  • Monochromator - used to disperse the light into its constituent wavelengths
  • Optics - may be designed to split the light beam so that the beam passes through sample compartments
• Spectrophotometers


  • Null balance Manual - Beckman DU-2 spectrophotometer (range from 190-1000nm)
  • Direct reading manual - Bausch and Lomb Spectronic 20 (range from 240-950nm)
• Parts of a UV-VIS spectrophotometer

  • Light source - halogen or tungsten lamps and deuterium lamps
  • Monochromator - composed of prism and slits
  • Sample and reference cells - contained sample and reference solutions, made of silica or quartz
  • Detector - two photocells serve the purpose of detector
  • Amplifier - to amplify the signals
• Cuvette


  A transparent container made of plastic, glass or quartz to hold the sample liquid for measurement
• When to use glass and quartz cuvettes

  • Glass cuvettes are used for measurements in the visible range from 320 to 2500nm
  • Quartz cuvette deliver precise results in the whole UV and visible range from 200 to 2500nm
• Precautions in using a spectrophotometer

  • Allowing the lamps and electronics to warm up
  • Using the correct wavelength
  • Wiping fingerprints and spilt sample off the outside of the cuvette before measuring
  • Carrying out the set-up procedure in the correct order
  • Performing calibration checks after set up
  • Closing the door to the cuvette compartment before reading the result
  • Cleaning up any spills inside the cuvette compartment
• Applications of spectroscopy


  • Qualitative and Quantitative Analysis
  • Detection of impurities
  • Quantitative analysis of all molecules that absorb light
  • Disruption of DNA double helix
  • Molecular temperature probes
  • Determination of equilibrium constants
  • Enzyme Kinetics
  • Analysis of mixtures of absorbing species
  • UV-VIS absorption as a diagnostic for NO in rocket plumes
  • Analysis of foods
  • Monitor ozone depletion
  • Determination of micelle structure
  • Drug dissolution
  • Spectral analysis of paintings
  • Art restoration / color matching
  • Light harvesting for solar energy
  • Determining wavelength response of fish eyes - Absorption spectra of retinal pigments
• Infrared spectroscopy


  The measurement of the interaction of IR radiation with matter by absorption, emission, or reflection
• Infrared ranges


  • Near IR 780 - 3000 nm
  • Medium IR 3.0 - 15 um
  • Far IR 15 - 300 um
• Spectroscopy


  The study of radiated energy and matter to determine their interaction
• Infrared light sources


  • Nernst Glower
  • Incandescent Lamp
  • Mercury Arc Lamp
  • Tungsten Lamp
  • Globar Source
  • Nichrome Wire
• Electromagnetic spectrum


  Includes ultraviolet (UV), visible, infrared (IR), radio, cosmic, and X rays
• Monochromator


  Produces a beam of light with an extremely narrow bandwidth, or light of a single color
• As wavelength gets shorter

  The electromagnetic radiation increases
• Types of monochromators


  • Prism
  • Diffraction grating
  • Filters
• Electromagnetic radiation


  A form of radiant energy released by electromagnetic processes such as visible light or invisible forms such as radio waves and x-rays
• Electromagnetic radiation


  • Exhibits a wide and specific range of wavelength, where its Energy is inversely proportional to its wavelength (distance between successive crests of a wave)
  • Exhibits a direction of propagation and wave-like properties (oscillations)
• Spectroscopic methods


  • Ultra-violet visible (UV-Vis) adsorption spectroscopy
  • Infrared (IR) absorption spectroscopy
  • Nuclear Magnetic Resonance (NMR) spectroscopy
• Applications of infrared spectroscopy

  • Qualitative fingerprint check for raw material identity and drug identification
  • Preliminary check for compound identity in synthetic chemistry
  • Characterize solid and semi-solid samples like creams and tablets
  • Fingerprint test for films, coatings and packaging plastics
  • Detect polymorphs of drugs
• Photon


  A tiny particle of light or electromagnetic radiation
• Terms


  • Frequency - number of times electric field radiation oscillates in one second (Hertz)
  • Wavelength - distance between successive waves (nanometer)
  • Amplitude - is the max. distance extends its middle position
• Spectrometry


  The application of spectroscopy which deals with the measurement of spectra