These instruments are used for a range of chemical analyses including determining the chemical composition of materials, quantifying the presence (or absence) of contaminants, and studying how materials break down chemically.
We currently have two FTIR instruments, a ThermoFisher Nicolet iS50, and a PerkinElmer Spectrum 2. These instruments use IR radiation to excite movement of atomic bonds in the sample, and then measure which wavelengths of IR radiation are absorbed by the sample as a function of these movements. The wavelengths absorbed can indicate which functional groups are present, as well as any potential fingerprint for the sample. Fingerprints are a unique combination of peaks that are particularly useful when matching an unknown sample against a spectral library.
ThermoFisher Nicolet iS50
The ThermoFisher Nicolet iS50 is a benchtop model FTIR. That has several different accessories that allow for analyzing different types of samples. We currently have the ones listed below.
The Nicolet iS50 comes with a built-in diamond ATR accessory. ATR—or Attenuated Total Reflectance—is our most commonly used accessory. The sample is placed on top of the crystal—infrared wavelengths are bounced up into the sample, back down through the crystal, and measured by the detector. This technique works with samples in a variety of forms—liquids, gels, powders, solids—anything that can be pressed into complete and even contact with the crystal by the pressure foot without scratching the crystal. This accessory is being used extensively by Research Associate Abigail Poe in her work on herbicide effects on historic building materials.
iN5 FTIR microscope
The iN5 FTIR microscope allows us to focus the IR beam on very small or specific sections of a sample—either in reflectance mode where the light IR beam is bounced off of the surface of the sample or in transmission mode, where the beam is shone through a sample such as a transparent liquid or thin section and measured. The iN5 microscope requires the use of liquid nitrogen to cool the detector for reliable results. Dr. Cooper is currently using this accessory to examine how cyanoacrylate adhesives, when applied to fossils, degrade over time.
This accessory is the only one that does not use IR wavelengths, but rather a laser. The movements that absorb the IR energy and are measured by the FTIR are most commonly asymmetric. The Raman module works using same principles but uses a higher-energy laser and measures symmetric bond movements. The addition of the Raman Module to this suite creates a complementary data set, and expands the types of materials that we can examine.
Smart Diffuse Reflectance FT-IR Accessory
Diffuse Reflectance FTIR (or DRIFTS) analysis uses IR energy directed down into a powdered sample and measures the wavelengths that are scattered out of the sample as a result. For this technique all samples must be powdered, and individually mixed with potassium bromide (KBr) powder. This FTIR technique requires more sample preparation but works better for certain types of samples and projects. DRIFTS was used extensively in the study of anti-efflorescence coatings on masonry.
PerkinElmer Spectrum 2
This FTIR instrument can be used both as a benchtop unit in the lab, and packed up to take out into the field. It is currently set up with a diamond crystal ATR accessory and laptop for the greatest range of flexibility.
The PerkinElmer Spectrum 2 was used by Research Associate Elizabeth Salmon in testing the depth of penetration of oils and cleaners into her samples of historic building materials.
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