Near-infrared spectroscopy wavelength range

Near infrared spectroscopy (NIRS), a technique based on absorption and reflectance of monochromatographic radiation by samples over a wavelength range of 400-2500 run, has been successfully applied for food composition analysis, for food quality assessment, and in pharmaceutical production control. NIRS can be used to differentiate various samples via pattern recognitions. The technique is fast and nondestructive method that does not require sample preparation and is very simple to use compared too many other analytical methods such as HPLC. The drawback of NIRS, however, is that the instrument has to be calibrated using a set of samples typically 20-50 with known analyte concentrations obtained by suitable reference methods such as FIPLC in order to be used for quantitative analyses. Simultaneous quantification of the... 

Near-infrared spectroscopy was used to quantitatively determine the phase composition of a compound capable of existing in two polymorphic forms even though the NIR spectra were fairly similar.79 Using a five-wavelength calibration model, nearly 100% recovery was obtained in a series of spiked calibration samples, with relative standard deviation values ranging from 0.1% to 0.9%. The authors concluded that the use of NIR spectroscopy... 

Near-infrared spectroscopy has been used to quantitate sulfathiazole Form-I and Form-Ill in binary physical mixtures in which one form was the dominant component.81 The spectra of each form exhibited sufficient differences that unique wavelengths of absorbance were easily attributable to each form. Excellent linearity in calculated versus actual compositions were obtained over the concentration range of 0-5% for either Form-I in Form-Ill, or for Form-Ill in Form-I. After considering appropriate calibration models, a limit of quantitation of approximately 0.3% was ultimately deduced. 

Lasers having wavelengths ranging from the deep uv to the near infrared have been used in Raman spectroscopy. In industrial laboratories, the most common laser is the Nd YAG operating at 1.06 pm. Increasingly, diode lasers or other lasers operating in the 750—785-nm region are encountered. These... 

Another consequence of the strong absorption properties of water is the spectral impact of the displacement of water by dissolved solutes. Generally, in absorption spectroscopy, the solvent is selected not to absorb over the wavelength range of interest. When the absorption properties of the solvent are negligible, any displacement of solvent molecules from the optical path by the dissolution of solute molecules has a negligible effect on the measured spectrum. For near-infrared spectra of aqueous solutions, however, the absorption spectrum depends heavily on the degree of water displacement by solutes in the sample. 

The common range for infrared spectroscopy is 10-12,800 cm (780-10 nm). Absorption spectra are described as a function of the wavenumber of the incident the wavenumber () is the reciprocal of the wavelength and has the advantage of being linear with energy. The infrared region can be divided into near-infrared, mid-infrared, and far-infrared regions. 

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