Near-infrared spectroscopy can be a workhorse technique for materials analysis in industries such as agriculture, pharmaceuticals, chemicals and polymers. A near-infrared spectrum represents combination bands and overtone bands that are harmonics of absorption frequencies in the mid-infrared. Near-infrared absorption includes a combination-band region immediately adjacent to the mid-infrared and three overtone regions.

All four near-infrared regions contain "echoes" of the fundamental mid-infrared absorptions. For example, vibrations in the mid-infrared due to the C-H stretches will produce four distinct bands in each of the overtone and combination regions. As the bands become more removed from the fundamental frequencies they become more widely separated from their neighbors, more broadened and are dramatically reduced in intensity. Because near-infrared bands are much less intense, more of the sample can be used to produce a spectra and with near-infrared, sample preparation activities are greatly reduced or eliminated so more of the sample can be utilized. In addition, long pathlengths and the ability to sample through glass in the near-infrared allows samples to be measured in common media such as culture tubes, cuvettes and reaction bottles. This is unlike mid-infrared where very small amounts of a sample produce a strong spectrum; thus sample preparation techniques must be employed to limit the amount of the sample that interacts with the beam.

Like the mid-infrared, combination bands and overtone bands correspond to the frequencies of vibrations between the bonds of the atoms making up the material. Because each different material is a unique combination of atoms, no two compounds produce the exact same near-infrared spectrum. Therefore, near-infrared spectroscopy can result in a positive identification (qualitative analysis) of each different material. In addition, the size of the peaks in the spectrum is a direct indication of the amount of material present. With modern software algorithms, near-infrared is an excellent tool for quantitative analysis.

NIR spectroscopy offers a practical alternative to time consuming, solvent intensive wet-testing methods and liquid chromatography techniques. NIR is ideal for quick and reliable raw material identification while also being a powerful analysis tool capable of accurate multi-component quantitative analysis. NIR is also ideal for process monitoring due to various sampling techniques and fiber optic sampling.

Advantages of NIR include:

• No sample preparation
• Can sample through glass and packaging materials
• Nondestructive measurements
• Fast, sample throughput accurate, reliable analysis
• Reduced costs
• Increased (can analyze 10 times more samples in a day)
• Remote sampling with low cost fiber optics