Worksheet: UV–Vis Spectroscopy Methods

In this worksheet, we will practice choosing a UV–vis spectroscopic method and comparing the features and limitations of different spectrometers.


Basic UV-Visible spectroscopy is designed to analyze samples in what phase?

  • AGas phase
  • BSolid (or suspension) phase
  • CPlasma phase
  • DSolution (or liquid) phase


Which of the following statements about UV-Visible spectrophotometers is not true?

  • AA diode array detector eliminates the need for a monochromator.
  • BDeuterium or tungsten lamps are commonly used as light sources.
  • CSingle-beam and double-beam instruments contain a filter for selecting one wavelength at a time.
  • DA simultaneous UV-Vis instrument contains mirrors and a monochromator in order to allow simultaneous detection at various wavelengths.


Which one of the following cannot be detected by fluorescence or phosphorescence spectroscopy?

  • AEnvironmental pollutants
  • BVitamins
  • CPharmaceuticals
  • DUncomplexed metal ions


Turbidimetry and nephelometry are analytical methods based on which of the following?

  • APhoton absorption
  • BPhoton emission
  • CNuclear repulsion
  • DLight scattering
  • EParamagnetism


How does turbidimetry differ from nephelometry?

  • ANephelometry measures the total metal ion, or inorganic, content; turbidimetry measures total organic content.
  • BNephelometry measures the decrease in transmittance of incident radiation; turbidimetry measures the intensity of scattered radiation.
  • CTurbidimetry measures the total metal ion, or inorganic, content; nephelometry measures total organic content.
  • DTurbidimetry measures the decrease in transmittance of incident radiation; nephelometry measures the intensity of scattered radiation.
  • EThe terms are synonymous; there is no difference.


Flame atomic absorption measures absorption of radiation of analytes in which phase?

  • ALiquid (neat) phase
  • BSolid phase
  • CAqueous phase
  • DGas phase
  • EPlasma phase


Why are flourescence and phosphorescence spectra measured at a 90 degree angle to the source?

  • ABecause the monochromator directs the light at a 90 degree angle.
  • BBecause the sample cell is darkened on two adjacent sides.
  • CBecause the process of fluorescence and phosphorescence are too intense to observe directly.
  • DTo ensure that incident (source) photons are not observed.
  • ETo make the overall instrument smaller.


Why is fluorescence spectroscopy often carried out in a liquid nitrogen environment?

  • AThe monochromator slows down the radiation before it hits the sample.
  • BPhosphorescent molecules tend to also have explosive properties.
  • CThe detector requires lower temperatures for operation.
  • DPhosphorescence is more likely to occur at low temperatures in a viscous medium.
  • EThe source radiation can overheat and destory the analyte.


In size exclusion chromatography, what happens to the larger particles?

  • AThey become oxidized as they move through the column.
  • BThey are broken down into smaller particles.
  • CThey remain on the column longer than smaller particles.
  • DThey elute first, before smaller particles.
  • EThey bind permanently to the stationary phase.

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