An Introduction to FTIR

FTIR stands for Fourier Transform Infrared. FTIR is a newer form of infrared spectroscopy, which is used to identify both organic and inorganic substances and can be used on solids, liquids and gases. In addition to identifying unknown compounds, infrared spectroscopy can also determine the amount of an individual compound in a given substance.

Infrared Spectroscopy

• The original method of infrared spectroscopy was dispersive. In this form of spectroscopy, the infrared light was separated, or dispersed, by a prism. The individual frequencies were then passed through the sample. The process was much slower than FTIR, which scans all frequencies at one time using an interferometer.

Interferometer

• According to the "Handbook of Instrumental Techniques for Analytical Chemistry," the Fourier transform system has three components: the radiation source, the interferometer and the detector. The interferometer is what makes FTIR different from other forms of spectroscopy. It consists of a beam splitter, a fixed mirror and a moving mirror. First, the beam from the radiation source passes through the beam splitter and is divided into two beams. One beam is reflected of the fixed mirror, the other off the moving mirror. The beams then reconnect in the beam splitter and create interference. The interference is measured and a graph called an interferogram is produced. This contains the measurements for all the infrared frequencies.

Detector

• The beam from the interferometer is then passed through the solid, liquid or gas sample. Some frequencies will be absorbed and others will pass through or be reflected, depending on the substance. "Introduction to Fourier Transform Infrared Spectrometry" states that this measurement is then sent to a computer, along with the interferogram, where the final calculations, known as the Fourier transformation, are completed. After the Fourier transformation, the spectrum of the sample is presented to the user for further analysis.

Advantages of FTIR

• There are many advantages to using FTIR as opposed to the other methods of infrared spectroscopy. The main benefit is that FTIR is a non-destructive technique and preserves the sample. In addition, it's much faster than earlier techniques. According to "Thermo Nicolet: Introduction to Fourier Transform Infrared Spectrometry," FTIR technology can collect a scan every second. FTIR analysis is also more sensitive and precise than other methods of infrared spectroscopy. FTIR is a simple machine with only one moving part.

Uses of FTIR

• FTIR has many practical uses. According to "Fourier Transform Infrared Spectroscopy," FTIR can be used to analyze chemical spills, find and identify a contaminant or analyze an unfamiliar drug. It can be used in many fields, including public health and safety, law enforcement and medicine. The results of the FTIR analysis are compared to the spectrum of known compounds. If the compound is not already recorded, other tests may be necessary to determine what it is.