Fourier-Transform Infrared Spectroscopy
FT-IR operates by determining how a material interacts with infrared light. Certain infrared frequencies will cause the molecular bonds of a material to vibrate (resonate). Since different types of bonds vibrate at different frequencies, we can determine the identity of many materials by looking at the patterns of infrared absorbances (called a “spectrum.” This is particularly useful for organic components like plastics, paints, and drugs.
With the microscope attachment to our FT-IR, we can measure the infrared spectrum of even a single microscopic crystal of any material. Here is the spectrum of a single crystal of an unknown white powder submitted to us. (Fig. 1)
The spectrum was readily identified as methamphetamine. The process took less time than a commercial break from the TV show “CSI”. (Fig. 2)
Scanning Electron Microscopy with Energy-Dispersive X-ray Spectrometry (SEM-EDX)
SEM-EDX is a combination of two approaches to analysis. A scanning electron microscope (SEM) uses an electron beam to view a sample, compared to a normal microscope that uses light. The higher energy of the electron beam permits viewing at much higher magnifications than are possible with light. Energy dispersive x-ray spectrometry takes advantage of the phenomenon that when a material is irradiated with a high-energy electron beam, the sample will emit x-rays. The x-rays have energies that are characteristic of the elements being irradiated. This permits the identification of the elements present in anything that we can view in the SEM.
Sometimes small particles are observed in beverages or drug solutions where they don’t belong. To correct the problem, the manufacturer needs to know what the particles are. Here is a tiny particle found in a water bottle. (Fig. 3)
The spectrum was identified as rust (iron oxide). The manufacturer was able to locate the corroding metal fitting and replace it. (Fig. 4)
Nuclear Magnetic Resonance (NMR)
Nuclear magnetic resonance is a technique used to identify or to characterize a chemical or mixture of chemicals. In this test, a sample is exposed to a strong magnetic field and a weak, oscillating magnetic field. The oscillating field causes the atoms within the sample to produce an electromagnetic signal that is characteristic to the atoms’ nuclei. Because this signal shifts in response to bonds with neighboring atoms, the molecular structure of a sample can be determined from the resulting NMR spectrum.