Temperature-dependent near-infrared (NIR) spectroscopy has been proposed and used in the quantitative analysis of multi-component mixtures and the understanding of the interactions in solutions. Mutual factor analysis (MFA) was developed, in our previous work, to detect glucose content in aqueous solutions and serum samples using the NIR spectra measured at different temperatures. The essence of the algorithm is to extract and compare the spectral component, named as standardized signal (SS), mutually contained in the spectral data of different samples. The relative quantity of SS can be used to build the calibration model for quantitative analysis. Furthermore, the spectral information of water can be used for the analysis, because the change of the water spectrum with temperature is a reflection of the change in glucose content. In this work, serum samples with low glucose concentration were prepared and measured at the temperature range of 30~60℃ with a step of 5℃. The feasibility of MFA in the quantitative determination of low concentration samples was further studied. Serum solutions with glucose content of 1.0~15.0 mmol/L and 0.0~1.0 mmol/L were prepared, respectively. Before calculation of MFA, continuous wavelet transform (CWT) was used to improve the resolution of the spectra. The results show that MFA can achieve an accurate quantification of the glucose content. The linear correlation coefficients (R) of the calibration models between the relative quantity of SS and the concentration of glucose are 0.9923 and 0.9895, respectively, and the root-mean-squared error of prediction (RMSEP) are 0.35 and 0.07 mmol/L, respectively. The relative error of predicted concentration of samples in the validation set obtained from the calibration model of samples with a concentration of 1.0~15.0 mmol/L are in the range of -12.00%~5.64%, which are in a reasonable level for clinical uses. Temperature-dependent NIR spectroscopy combined with MFA may be a potential way for detecting the micro-content components in complex aqueous systems.

Key words: near-infrared spectroscopy, temperature effect, mutual factor analysis, glucose detection, serum