Preparation of Samples for IR Spectroscopy: Other Methods

Solid samples can be prepared for IR examination by one of several methods:

• A mull is prepared by grinding the sample with mineral oil and sandwiching the resultant paste between sodium chloride plates.
• The solid can be dissolved in a solvent and placed in a special cell, called a solution cell, which is made of sodium chloride. This gives what is called a solution spectrum.
• A KBr pellet is prepared by grinding the solid sample with solid potassium bromide (KBr) and applying great pressure to the dry mixture. Again, KBr is chosen because it is transparent to infrared radiation. If the pellet is prepared properly, one can actually see through it, as through a pane of glass. We prepared a movie of how to prepare a KBr pellet in c1993. This movie shows the use of a different mechanical press than we currently use; the rest of the film is still valid and useful to a beginner learning how to prepare a KBr pellet.
  • movie on how to prepare KBr pellets in the IR sample preparation movie: Section on how to prepare KBr pellets - 14 min 15 sec into the film