Near-infrared (NIR) spectrophotometry is an analytic spectroscopic technology that measures a substance’s characteristic spectrum in near-infrared regions (circa 780-2,500 nm in wavelength; circa 12,800-4,000cm-1 in wavenumber) and extract correlated information with suitable chemometric algorithms to conduct qualitative and quantitative analyses on substances.

NIR spectra are dominated by C-H, N-H, O-H and S-H overtone resonances and combinations of fundamental vibrational modes. NIR bands are much weaker than the fundamental mid-lR vibrations from which they originate. Besides, NIR bands are always overlapping. Therefore, it is inappropriate to directly analyze the NIR spectra. Instead, suitable validated mathematical treatment of the data is required before qualitative and quantitative analyses.