FTNIR

FTNIR stands for Fourier Transform Near-Infrared spectroscopy, a form of near-infrared spectroscopy that uses Fourier transform techniques to convert an interferogram into a spectrum. It measures absorption or transmission of near-infrared light, typically in the range of about 780 to 2500 nanometers, to provide information about molecular vibrations, primarily overtones and combination bands of bonds such as CH, NH, OH, and SH.

In FTNIR, a broadband light source illuminates a sample through an interferometer, usually a Michelson-type device. The resulting interferogram is recorded by a detector, often based on InGaAs technology, and a Fourier transform converts it into a conventional spectrum. The method can be applied in transmission, reflectance, or attenuated total reflectance (ATR) configurations, and is capable of rapid, high-signal measurements with good multiplex and throughput advantages.

Instrumentation commonly includes compact, benchtop or portable spectrometers, fiber-optic probes for in situ analysis, and software for chemometric data processing. FTNIR is widely used for rapid, non-destructive quantitative and qualitative analysis, often requiring calibration models developed with multivariate methods such as principal component analysis or partial least squares regression.

Applications span pharmaceuticals (content uniformity, moisture, active ingredient quantification), food and agriculture (moisture, fat, protein, sugar content), polymers and materials (composition and additives), and process analytics for real-time quality control. Advantages include minimal sample prep, non-destructive testing, and fast data acquisition, while limitations include the need for robust calibration, potential spectral overlap, and interference from water in some samples.