PerkinElmer Spotlight 150, User Manual

Page: 56 / 107

56 . Spotlight 150 User's Guide
Separating by aperturing
Powders and other particulate solids may contain several different components. Instead of
separating them, use the infrared aperture to isolate the component you want to sample:
1. Spread the sample out with a probe so that you can visually distinguish the
components.
2. Looking at the Monitor Visible window, find a particle of the component you want to
sample.
3. Center this particle in the field of view.
4. Adjust the infrared aperture until only the particle that is of interest is visible.
You can easily pick up extremely small particles and transfer them with a very fine-pointed
tungsten needle. Scoring the surface of the salt plate with the needle makes a simple map to
help you positively identify the particles under the microscope.
Transferring with a tungsten needle
When necessary, sharpen the tungsten needle.
Nujol or fluorolube mulls
Suspending fine particles of a solid sample in nujol or fluorolube reduces or eliminates the
surface reflections that can distort absorption measurements. These oils also reduce the
amount of radiation lost to reflection or scattering.
If the film is thin enough, you can correct the spectrum for the presence of the oil by
subtracting a spectrum of the pure liquid. It is difficult, however, to obtain the correct
thickness for a good subtraction.
Fibers
You can roll fibers to flatten them (see
Flattening Solids
on page 51), or they can be pressed
in a diamond anvil cell (see
Polymers
on page 53).
Fibrous Solids
If a fibrous sample, such as paper, is too thick, tear it and examine the torn edges. The
edges contain single fibers and thin clumps of fibers.