Fourier-transform Infrared (FTIR)

Infrared spectroscopy (ExoScan 4100, Agilent; Vertex 70, Bruker) studies the interaction of electromagnetic radiation with the atomic vibrations of a matter by absorption, emission, or reflection. Historically, IR spectroscopy has been commonly used for the investigation of organic materials and hydrous phases. It is therefore a well-established method for classifying, for instance, binding media. To perform a conventional measurement (so-called transmission mode), a thin or powdered sample in the form of a pellet is placed in the beam pass and the amount of transmitted light detected as a function of wavelength or frequency, producing an infrared spectrum. For the production of these pellets, microsampling (~ 1 μg) of the desired object is needed, where the extracted material is mixed with potassium bromide (KBr) in a 1:200 ratio (for more details see FTIR - experiments in macrochamber). The use of KBr as a carrier for the measurement is necessary, because it is optically transparent for the light in the range of an IR measurement. To reduce the sample size, special diamond cells were developed. Rapid technological progress in this field led to the appearance of non-destructive methods such as Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) (see ExoScan 4100; Vertex 70) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) (see ExoScan 4100) including spectrometers equipped with fibre-optics for the study of surfaces, and synchrotron-based FTIR spectroscopy. The miniaturisation of infrared sources and detectors brought a new generation of portable FTIR spectrometers, for example a hand-held ExoScan.