NIR briefly explained…

NIR is the abbreviation for near-infrared. Near-infrared spectroscopy is a physical method for the non-destructive analysis of mostly organic molecular compounds. NIR works with light between approx. 800 and 2,500 nanometers wavelength and thus lies between the visible spectral range (VIS) and the mid-infrared (MIR).

When NIR radiation is absorbed, the molecules are excited to vibrate. Information about the molecular composition is then read from the reflected (or transmitted) spectra. They can be used both to identify substances and to quantify components in mixtures.

In contrast to MIR, NIR spectroscopy measures harmonics and combination vibrations of molecular groups. The resulting spectra are then analyzed using mathematical-statistical and chemometric methods (e.g. PCA, PLS).

• Method that has been established and used for decades.
• Light-based and therefore non-destructive and contactless analysis possible.
• Perfect technology for moisture and water content analysis.
• No radiation or laser protection measures required.
• Also images some physical parameters, e.g. granularities.
• Less expensive than other spectroscopy technologies.

Of course, there are also limitations: If very high accuracies / specificities or low detection limits (e.g. ppm) have to be achieved, other technologies are better suited, e.g. Raman or FT-IR spectroscopy. Also, the very prominent OH signal is sometimes more disturbing than beneficial, in which case it is better to work with Raman.

The numerous areas of application for NIR spectroscopy range from plastic sorting in recycling and identity verification in incoming goods to process control in the chemical and pharmaceutical industries and the identification of narcotics by authorities and organizations with security tasks.

NIR-Spectrometer