Quantitative Spectroscopy

Nearly all objects absorb light of one range of wavelengths or another and require specialized equipment to analyze the wavelengths absorbed. Demonstrations with both absorbance and emission spectroscopy can be done visually using MicroLab’s hand-held visual spectrometer or, for solution quantification and characterization, students can use MicroLab’s patented FASTspec technology built into our FS interfaces.

Because of the unique construction of the FASTspecTM instrument with 16 wavelengths of LEDs ranging from 360 nm to 880 nm, it simultaneously measures:

  1. Transmittance/Absorbance
  2. Turbidity (the amount of the LED beam light passing through the medium, or solution cloudiness) and solution nephelometry (the amount of light scattered by the medium) at 45o or usually at 90o to the 880 nm wavelength beam.
  3. Scatter, at 90o or 135o to the LED beam
  4. Fluorescence at 90o angle of incidence

This is done for all 16 wavelengths sequentially in less than a minute. No other instrument on the market can accomplish this.

Absorbance and Fluorescence are excellent methods to monitor the appearance or disappearance of a reacting species.  Repeating the 16-wavelength scan at intervals of 5-120 seconds lets students ‘watch’ as reactions are occurring.  The plots below show kinetic data collected from a crystal violet reaction with sodium hydroxide.  The data was fit by simply clicking on the desired tab at the top left of the screen to obtain fits for zeroth order, first order or second order behavior.  Students then compare all three fits to determine that this reaction is first order with respect to crystal violet.  Because they can set this experiment up and run it in very little time, students have time to test several concentrations of sodium hydroxide as well to determine its rate order.  For more information and other experiment ideas, please check out the Absorption Spectrophotometry page.