PerkinElmer Spotlight 400 Series, User Manual

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54 . Spotlight 400 Series User’s Guide
Techniques for Preparing Samples
This section describes some useful techniques for preparing various types of samples.
Flattening Solids
Flattening samples by pressing or squeezing often enables you to make thick samples thin
enough to give good infrared spectra. Because the samples are usually quite small, only
moderate force is necessary.
Rolling with the roller knife
The roller end of the roller knife provided in the microsampling tool is one of the simplest
and most effective devices for flattening samples. It is especially useful for flattening fibers
or particles.
You can treat different types of sample in different ways:
• If the sample is soft, you can roll it on a small salt window.
• If the sample is hard, you can roll it on a hard surface, such as glass or metal. A flat,
black cap from a jar makes a good surface for rolling a light-colored sample.
• If you roll the sample on a small, flat piece of metal you can view it and collect spectra
in reflectance or diffuse reflectance mode. Samples rolled on windows transparent to
infrared can be examined in transmittance.
•
If you flatten fibers on a glass microscope slide, they can then be peeled off and
mounted either on a window or over the aperture for the microscope slide.
Squeezing with a pellet press
You can squeeze samples between the polished anvils of a KBr pellet press without KBr. To
collect the spectra use one of the following methods:
•
Peel the flattened sample off the anvil with a probe or knife and place it on a sample
mount. Collect the transmittance spectrum.
•
Leave the sample on the polished anvil and collect the reflection spectrum. Use a clean
area of the anvil as the reference.
Using a diamond anvil cell
See the procedure in
Polymers
(page 56) for information on flattening samples with a
miniature diamond anvil cell.
Compressing between infrared transmitting windows
Pressing two windows together, with the sample between them, compresses the sample.
This also provides optical contact between the windows and the sample, reducing surface
scattering.
Windows made of NaCl or KBr are relatively soft. If your sample is hard, or if it is wet, use
BaF
2
or ZnSe.