Environmental Engineering Reference
In-Depth Information
- Measuring super lattices in multilayered epitaxial structures
- Determining the thickness, roughness, and density of the film using glancing
incidence X-ray reflectivity measurements
• Make textural measurements, such as the orientation of grains, in a polycrystal-
line sample.
13.2.7 Fourier Transform Infrared Spectroscopy (FTIR)
FT-IR stands for Fourier Transform Infrared, the preferred method of infrared
spectroscopy. In infrared spectroscopy, IR radiation is passed through a sample.
Some of the infrared radiation is absorbed by the sample and some of it is passed
through (transmitted). The resulting spectrum represents the molecular absorption
and transmission, creating a molecular fingerprint of the sample. Like a fingerprint
no two unique molecular structures produce the same infrared spectrum. This
makes infrared spectroscopy useful for several types of analysis.
FTIR spectrometers (Fourier Transform Infrared Spectrometer) are widely used
in organic synthesis, polymer science, petrochemical engineering, pharmaceutical
industry, and food analysis. In addition, since FTIR spectrometers can be hyphen-
ated to chromatography, the mechanism of chemical reactions and the detection of
unstable substances can be investigated with such instruments.
Fourier Transform Infrared (FT-IR) spectrometry was developed in order to
overcome the limitations encountered with dispersive instruments. The main diffi-
culty was the slow scanning process. A method for measuring all of the infrared
frequencies simultaneously, rather than individually, was needed. A solution was
developed which employed a very simple optical device called an interferometer.
The interferometer produces a unique type of signal which has all of the infrared
frequencies “encoded” into it. The signal can be measured very quickly, usually on
the order of one second or so. Thus, the time element per sample is reduced to a
matter of a few seconds rather than several minutes.
13.2.8 Matrix-Assisted Laser Desorption/Ionization Time-of-
Flight Mass Spectrometry (MALDI-TOF)
Matrix-assisted laser desorption/ionization time of-flight mass spectrometry
(MALDI-Tof-MS) has advanced from early-stage research toward applications of
real clinical relevance only within the last 10 years. MALDI-Tof-MS has become a
popular and versatile method to analyze a range of macromolecules from biological
origin from cells to tissues. Its ability to desorb high-molecular-weight thermo
labile molecules, its high accuracy and sensitivity, combined with its wide mass
range (1-300 kDa), make MALDI-Tof-MS a promising method for the clinical
