A reference-wavelength-based method for improved analysis of near-infrared spectroscopy.

Near-infrared (NIR) spectroscopy has been widely used in many industrial applications. It also has tremendous potential for trace element detection and noninvasive human physiological measurements. In NIR spectroscopy, however, the measurement precision is often dependent on temperature, measurement position, and sample status. In order to improve measurement precision, a method using spectral information at a reference wavelength is developed in this paper. Based on the displacement effect between solvent and solute molecules in a solution, the signal at the reference wavelength is used as an internal reference to correct the spectrum of the sample under test. As an example, the spectra of glucose aqueous solutions under different temperatures are measured, and our method for eliminating the temperature disturbance is evaluated. The experimental results obtained show that the relative error of glucose concentration prediction is 330% per degree before the spectrum correction. After the correction, the relative error is reduced to 5.12%, and the error is no longer dependent on temperature. As the displacement effect can be found commonly in various solutions, the method described in this work may be used to improve the accuracy of spectral analysis of many other solutions.