Fourier Transform Infrared (FTIR) Spectrometer is a powerful analytical instrument used to identify and study the chemical composition of materials by measuring their absorption of infrared light.

Unlike traditional dispersive IR instruments, an FTIR utilizes an interferometer, typically a Michelson design with a beamsplitter and moving mirror. This setup creates an interferogram—a complex signal of light intensity versus mirror position. The core principle is that all infrared frequencies are measured simultaneously, dramatically improving speed and sensitivity. This key advantage is known as the Fellgett or multiplex advantage.

The collected interferogram is not an immediately interpretable spectrum. It is converted into a familiar infrared absorption spectrum (intensity vs. wavenumber) through a mathematical process called the Fourier Transform, performed by a computer.

The resulting spectrum acts as a molecular “fingerprint.” Different chemical functional groups (e.g., C=O, O-H, N-H) absorb infrared light at characteristic frequencies, allowing for the identification of organic, inorganic, and polymeric materials.

FTIR spectroscopy is renowned for its high speed, precision, and signal-to-noise ratio. Its applications are vast, spanning chemical analysis, pharmaceutical quality control, forensic science, environmental monitoring, and materials science, making it an indispensable tool in modern laboratories.