Chromatography Techniques and Spectrometry

Infrared Spectroscopy or Vibrational Spectroscopy

The interaction of infrared radiation with matter is involved by Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy). Mostly based on absorption spectroscopy, it covers a range of techniques. It can be used to identify and study chemicals as with all spectroscopic techniques. The state of the Samples may be either solid, liquid, or gas. Infrared spectrometer (or spectrophotometer) is an instrument used to produce an infrared spectrum by the method or technique of infrared spectroscopy. On the vertical axis vs frequency or wavelength on the horizontal axis of an IR spectrum can be visualized in a graph of infrared light absorbance (or transmittance).  Reciprocal centimetres (sometimes called wave numbers) are the typical units of frequency used in IR spectra, with the symbol cm−1. Micrometres are the Units commonly given in IR wavelength, symbol μm, which are related to wave numbers in a reciprocal way. Fourier transform infrared (FTIR) spectrometer is a common used laboratory instrument. Two-dimensional IR is also possible as discussed below.

Considering the relation to the visible spectrum, usually the three regions that are classified infrared portion of the electromagnetic spectrum are; the near- infrared, mid- infrared and far- infrared radiations. Excite overtone or harmonic vibrations are don by the higher-energy near-IR, approximately 14000–4000 cm−1 (0.8–2.5 μm wavelength). To study the fundamental vibrations and associated rotational-vibrational structure, approximately 4000–400 cm−1 (2.5–25 μm) may be used by the mid-infrared spectroscopy. Lying adjacent to the microwave region the far-infrared spectroscopy, approximately 400–10 cm−1 (25–1000 μm, has low energy and may be used for rotational spectroscopy. Based on the relative molecular or electromagnetic properties the names and classifications of these sub regions are conventions, and are only loosely arranged.