Biospectroscopy, the technology applied by Molecular Biometrics, is an optical-based analytical technology that provides a simultaneous and integrated measure of all metabolic activities taking place in a biological sample. Each resulting spectrum translates into a unique “fingerprint” or “metabolomic profile” that defines the metabolic status of the target sample and thus the biological host whence the sample was procured.
Multiple characterization tools, both chromatographic and spectroscopic, exist in the application of metabolomics. Molecular Biometrics enlists the use of capillary electrophoresis (CE), mass spectrometry (MS), nuclear magnetic resonance (NMR) spectroscopy, Raman and near infrared (NIR) spectroscopy. The latter of these, NIR spectroscopy, has become the primary instrumentation candidate in Molecular Biometrics’ technology platform.
An In-depth Look into Near Infrared (NIR) Spectroscopy
Near Infrared refers to the region of light immediately adjacent to the visible range, falling between 750 and 3,000 nanometers (nm = nanometers or 1/1000000000 of a meter) in wavelength. In contrast, the human eye can detect wavelengths between 400nm to approximately 780nm, which appear as colors of blue to deep red.
According to the principles of quantum physics, molecules may only assume discrete energy levels. Similar to the vibrating string of a musical instrument, the vibration of a molecule has a fundamental frequency, or wavelength, as well as a series of overtones. The unique spectrum shape for any material is the result of the absorbance of the characteristic fundamentals and overtones. Near-infrared spectra are a result of anharmonic overtone and combination bands due to vibrations of O-H, C-H, N-H and C=O groups. The graph on the following page depicts the prominent absorption bands as they relate to the overtone and combination bands of the fundamental vibrations occurring between 900 – 1700nm.
Near infrared absorption bands visible between 900 – 1700nm
Near infrared spectroscopic analysis is simple – expose a target sample (e.g. biological fluid) to a range of light wavelengths, and measure the characteristic absorbance spectrum of the sample. Since the molecular structure of most compounds is very complex, the resulting spectra are actually the result of many overlapping peaks and valleys. In addition, the amount of NIR light absorbed is directly proportional to the quantity of molecules present in the sample. Generally speaking, persons performing NIR analysis must then identify and characterize specific features in the spectra by means of statistical methods. Chemometrics and bioinformatic software is designed to accomplish this task.
Applications of NIR Spectroscopy
NIR spectroscopy’s industrial and medical applications have expanded since its first application in the 1950s. Because NIR spectroscopy is simple to use, can be easily compacted into a portable device that requires little maintenance, and is relatively inexpensive, it has played an increasingly important role in industry. In particular, NIR spectroscopy is widely incorporated into quality control protocols for the food, animal feed, pharmaceuticals and textile industries.