Next: 2.4 Sampling Techniques Used
Up: 2. Introduction to Infrared
Previous: 2.2 Group Regions
2.3 Common Sampling Modes
There are many techniques for the measurement of IR spectra. The basic
ones utilize the fact that the alkali salts are transparent in large
portions of the IR part of the electromagnetic spectrum. This section
briefly summarizes some of the common techniques.
- KBr pellet
- good for powders; a few milligrams of the sample power
and an excess of KBr are finely ground and pressed under high pressure
into a pellet. This is a useful and very general method for solids.
- Salt cells:
- good for organic liquids; the liquid is placed into
a reservoir milled in alkali salt windows.
- Nujol mull:
- the material of interest is suspended in oil, such
as mineral oil, and the resulting paste is spread thinly on a salt
window to form a film. This is a good technique for oils and waxy
solids that do not press well into pellets.
John S. Riley, DSB Scientific Consulting