With the continuous development of spectral analysis technology, on-line spectral analysis technology has been widely applied. It can real-time monitor the key links in the process of liquid transportation, and provide real-time guidance for reliable and efficient liquid delivery. In the process of non-sampling real-time measurement of the solution in a flexible conveying tube, the accuracy of the spectral analysis is reduced due to the differences in optical parameters of the flexible conveying tubes. Therefore, this paper studies the effects of differences in flexible conveying tubes on on-line spectral analysis. A standard solution calibration method was proposed to suppress the interference caused by the differences of flexible conveying tubes based on the modified Lambert Beer's law. The calibrated spectral data is modeled by partial least squares regression to reduce the analysis error introduced by the optical differences of the flexible conveying tubes. An experiment was designed to verify the feasibility of the method by using a mixed solution of Intra-lipid and India-Ink as an analytical sample and using a polyvinyl chloride (PVC) material tube as a flexible conveying tube. The experimental results show that the method of calibrating the differences of the flexible conveying tubes by the standard solution is feasible, and effectively inhibits the impact of the differences of the conveying tubes on the online spectral analysis.
In the spectral analysis for biological fluids compositions, the sensitivity of trace compositions reflected in the spectral is very small, which results in the low measurement accuracy. This paper proposes a “Multi-dimension and Multi-mode spectroscopy method” to improve the measurement accuracy of trace compositions by two aspects of spectral acquisition and data processing: measuring the biological fluids sample at multiple modes so that multiple spectral for each sample can be obtained which will carry more information about trace compositions, then connecting these spectral to increase the spectral data dimension that is equivalent to increase the number of constraint equations in the modeling process, the error will be reduced through more constraint equations. An experiment was designed: taking the cholesterol concentration (2.57-8.1mmol/L) in blood plasma as the tested object, the blood plasma was irradiated with tungsten lamp and ultraviolet light source respectively, ultraviolet light stimulates blood plasma can produces fluorescence, the obtained transmission spectrum and fluorescence spectrum were rearranged to build the model. Experimental results showed that the analysis accuracy of cholesterol had been significantly improved. This research provided a new thinking of the analysis for biological fluids trace compositions.