L-Ascorbic Acid Prediction in Aqueous Solution Based on FTIR-ATR Terahertz Spectroscopy

The feasibility of using attenuated total reflectance-terahertz (ATR-THz) spectroscopy for quantification of L-ascorbic acid (L-AA) in aqueous solutions was investigated. The spectra of 55 samples of L-AA solution ranging in concentration from 0-21% were acquired using Terahertz-based Fourier transform infrared (THz-FTIR) spectrometer. Spectral absorbance in the range 20 to 400 cm-1 was used in this analysis. Full spectrum partial least squares (FS-PLS) regression was used to develop and validate the calibration model for determination of L-AA. The result showed that using the pre-processing of Savitzky-Golay first derivative spectra, prediction resulted in the lowest root mean square error of prediction (RMSEP) = 2.791%. A ratio of standard deviation to prediction error (RPD) value of 4.48 was obtained.