Quantitative analysis of ternary isomer mixtures of saccharide by terahertz time domain spectroscopy combined with chemometrics

Abstract

Terahertz time-domain spectroscopy (THz-TDS) provides potential for analysis of sample features which cannot be detected by other commonly used spectroscopic techniques. This paper presented a novel THz-TDS approach combined with chemometrics to analyze ternary saccharide isomer mixtures including d-(−)fructose, d-(+)galactose anhydrous, and d-(+)mannose. The infrared (IR) and THz absorption spectral features of the saccharide isomers were compared and discussed. Support vector regression (SVR) and partial least squares (PLS) were applied for quantitative modelling on the collected THz spectra of the ternary isomer mixtures. The performances of the preprocessing methods of Savitzky–Golay (S-G) smoothing and wavelet transform were investigated for the PLS and SVR models. To achieve a reliable and unbiased estimation, bootstrapped Latin partitions (BLPs) was applied for statistical cross-validation. Multiway ANOVA was applied to find out significant factors and interaction between different factors. Results show that both PLS and SVR are applicable for the three compounds, d-(−)fructose, d-(+)galactose, and d-(+)mannose, in mixtures. For example, the correlation coefficient (R2) of the three saccharide isomers between experimental and predicted values in cross-validation set are 0.969, 0.903, and 0.938, respectively. As a conclusion, the proposed method can be feasible for the analysis of the ternary saccharide isomer mixtures and have potential for the analysis more complex mixtures in nutritional analysis.