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Nutrition for Optimal Wellness

FTIR and NIR Spectroscopy and Their Applications

By Heidi Li, Research & Development [former], NOW Foods
In recent years, the authentication of natural foods, herbal medicines and dietary supplements has become a major challenge for the analytical chemist because these products often contain a wide range of herbs and other natural products. Regulatory authorities, food processors and consumers are increasingly demanding that manufacturers screen those products to be sure that they have not been adulterated with contaminants or cheaper ingredients.
Authenticity is an important quality criterion for nutritional and pharmaceutical formulation function and safety. Typically, analytical authentication strategies focus on specific molecular markers, or on recording compositional profiles or “fingerprints”. For this reason, spectroscopic techniques are very attractive tools since these techniques  are simpler and faster and can be more easily implemented during routine analysis. At NOW Foods, numerous analytical methods using different analytical instruments have been developed for this purpose, which include High Performance Liquid Chromatography (HPLC), Gas Chromatography (GC), Fourier Transform Infrared (FTIR), Near Infrared (NIR), etc. Infrared (IR) spectroscopy (FTIR and NIR spectroscopy) has been utilized as a primary identification tool to authenticate raw materials and final products.
IR spectroscopy is an analytical technique used to identify organic (in chemistry organic means carbon-based), as well as some inorganic, materials. It can be utilized to identify components of an unknown mixture in solid and liquid forms. Within the infrared wavelengths of light, the waveband between 4 ~ 400 cm-1  is categorized as far infrared, between 400 ~ 4,000cm-1 is categorized as mid infrared and between 4,000 ~ 14,000cm-1 is categorized as near infrared.
Mid infrared spectroscopy is useful to identify a variety of adulteration problems using experimental and statistical methods. FTIR looks at the mid infrared spectrum, and refers to the fact that the infrared spectra is obtained by collecting an interferogram of a sample signal with an interferometer. This interferometer measures all of the infrared frequencies simultaneously. The region between 1500 – 400cm-1 is referred to as the fingerprint region. Absorption bands in this region are generally due to intra-molecular phenomena and specify molecular composition and structure. These allow computerized data searches to be performed against reference libraries in order to identify substances. An FTIR spectrometer acquires and digitizes the interferogram, performs the fourier transform function, and outputs the spectrum with a higher energy throughput, as well as with excellent reproducibility and accuracy from the laser light source.
NIR is another rapid, reliable and non-destructive technique that is widely used for quality and processing control for the qualitative characterization of various products without using reagents or solvents. Near-infrared light ranges from 4000 to 14,000 cm-1 and is energetic enough to excite molecular overtones and combinations of vibrations to higher energy levels. NIR can generally penetrate much farther into a sample than mid infrared radiation. Therefore, near infrared spectroscopy is very useful in exploring bulk material with little or no sample preparation.
NOW Foods is using state-of-the-art spectroscopic methods to test our supplements.
Baulsir and Simler, 1996 C.F. Baulsir and R.J. Simler, Design and evaluation of IR sensors for pharmaceutical testing, Advanced Drug Delivery Reviews (1996), p. 191–203
Kemsley et al., 1996 E.K. Kemsley, J.K. Holland, M. Defernez and R.H. Wilson, Detection of adulteration of raspberry purees using infrared spectroscopy and chemometrics, Journal of Agricultural and Food Chemistry (1996), p. 3864–3870
G. Downey, J. Boussion and D. Beauchêne, J. Near Infrared Spectrosc.  (1994), p. 85
Downey et al., 2002 G. Downey, P. Mcintyre and A.N. Davis, Detecting and quantifying sunflower oil adulteration in extra virgin olive oils from the Eastern Mediterranean by visible and near-infrared spectroscopy, Journal of Agricultural