Fourier Transform Infrared Spectroscopy (FTIR) is a technique used to identify functional groups present in a sample. The sample is exposed to a narrow beam of infrared light at various wavelengths, and the absorption or transmission of the wavelengths is detected in the form of an infrared spectrum. This spectrum provides information pertaining to the types of bonds and the functional groups present in the material of interest.
XRF and XRD
X-ray fluorescence (XRF) is a technique used for elemental and chemical analysis. When a material is exposed to X-rays or gamma rays, the constituent atoms may ionize. This ionization consists of the ejection of an electron from one of the atom’s inner orbitals. The removal of an electron from an atom’s inner orbital creates an unstable electronic structure for the atom, and electrons from higher orbitals “fall” into the ejected electron’s place. As the electron “falls” into place, energy is released in the form of a photon that is equal to the energy difference between the two orbitals. The energy of the photons emitted is characteristic of the atom that emitted it. This technique thus allows for the identification of elements within a material.
X-ray diffraction is used to analyse the structure of crystalline materials. This microstructural analysis is used to identify the phases present in the material and determine unit cell dimensions.
Gas chromatography–mass spectrometry (GC-MS) combines the two analytical methods of gas chromatography and mass spectrometry. Gas chromatography allows for the separation of volatile compounds in a mixture based on their differing polarities. A GC column is used to separate the compounds within a mixture, followed by their detection via a mass spectrometer. The mass spectrometer ionizes the compounds as they elute from the column and produces a mass fragmentation spectrum of the ionized compound. This allows for the identification of compounds present in a mixture based on their mass fragmentation pattern.
During High-performace liquid chromatography (HPLC) a solvent moves through a closed column at a high pressure. These closed columns contain fine particles (1.7 to 5 µm) that ensures separation of the analyte. A mass spectrometer is fitted to the HPLC for detection of the individual components of the analyte. HPLC-MS is an important technique as most compounds are not sufficiently volatile for GC-MS.