Research and development of the hottest near infra

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Near infrared spectroscopy (NIST) is a non-destructive testing technology that uses the characteristics of light absorption, scattering, reflection and transmission to determine the content of its components. It has the advantages of fast, non-destructive, reagent free analysis, safety and efficiency, and can determine a variety of components at the same time. The application of near infrared spectroscopy in detection and analysis is a hot spot in recent years

in the process of developing near-infrared spectrometer, how to improve signal-to-noise ratio, wavelength accuracy, stability, etc. is the focus of equipment research and development. First of all, researchers and users often put it in a particularly prominent position in terms of improving signal-to-noise ratio. So, what is the signal-to-noise ratio? Why is it so important? Signal to noise ratio, also known as signal to noise ratio, refers to the ratio of signal to noise in an instrument. For near-infrared spectral analysis, because the instrument itself is based on the small fluctuation of spectral absorbance caused by the change of absorbant content, signal-to-noise ratio plays an important role. For example, when the content change of protein in food is less than 1%, at the strongest absorption wavelength, absorb 2: the degree of light changes by only 0.002 in the tensile test. When analyzing complex samples, it is often necessary to carry out various mathematical processing of spectral data, which requires calculation at the level of high absorbance. At this time, the importance of instrument signal-to-noise ratio is highlighted. Absorbance repeatability is a crucial index for near-infrared detection, which directly affects the quality of model establishment and the accuracy of measurement. It is generally required that the absorbance repeatability is better than 0.0004a. Therefore, in order to effectively improve the signal-to-noise ratio of products, generally we will start from three aspects: the receiver, appropriately increasing the spectral broadband and using tungsten lamp light source with higher luminous efficiency per unit area

in addition, wavelength accuracy and repeatability are also the focus of near-infrared spectrometer research. In order to ensure the effective transmission of calibration models between instruments, it is usually required that the wavelength accuracy in the long wave near-infrared range should be better than 1.0nm, and the accuracy in the short wave near-infrared range should be higher than 0.5nm. The realization of high wavelength repeatability is also related to the scanning speed. The scanning speed of near-infrared is dozens of times higher than that of UV-Vis photometer. In order to effectively improve the accuracy and repeatability of wavelength, we can start from solving the accurate positioning of grating and paying attention to the coefficient of thermal expansion between different materials

stability is indispensable to all analytical instruments, and the near-infrared spectrometer is no exception. At present, the near-infrared spectrum is basically a single beam type. The fluctuation of the light source and the drift of the receiver temperature are directly reflected in the spectral data. The optical design of double beam will effectively eliminate the drift of light source, receiver and other devices, and greatly improve the long-term stability of the instrument

in terms of the requirements of sample measurement accessories, the design of sample measurement accessories in the same situation is also different for different measurement objects. For example, the accessories used for diffuse reflectance spectrum acquisition include integrating sphere, polished rod probe, etc. In terms of absorbance, for the same NIR spectrometer, the guarantee of wavelength accuracy and absorbance accuracy is conducive to the establishment of an excellent calibration model. The instrument factor that affects the linear range of absorbance is mainly the detector. In addition, noise and stray light also have a certain impact. Finally, because the testing environment is generally the field environment, rather than the laboratory, the instrument needs a certain degree of protection, and the key components should be sealed and have the requirements of dust prevention, high temperature resistance and so on

near infrared spectroscopy technology can be used for the measurement of various forms of samples, including solid and semi-solid in addition to gas and liquid. This feature makes its annual average growth rate of 24%, which has the advantage of surpassing the traditional detection technology, and the elongation at break of ordinary polymer materials is mostly between 50% and 100%, which saves the detection cost and test time to a great extent. At the same time, we cannot ignore that although near-infrared spectroscopy has developed rapidly in recent years, it also has defects such as low signal-to-noise ratio and inapplicability of trace analysis. In order to realize the further development of near-infrared spectroscopy technology, researchers need to work together and make common progress

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