The spectral resolution of unknown mixture based on THz spectroscopy with self-modeling technique

• To obtain the THz spectra of pure components, SMCR was performed to resolve the THz data of mixture.
• Second derivative was employed to improve the purity of pure variables in resolution.
• SVD was used to predict the number of components in system.

This study aims at resolving the spectral profiles of pure components from the mixture THz data. A method based on simple-to-use interactive self-modeling mixture analysis (SIMPLISMA), one of self-modeling curve resolution (SMCR) techniques, was put forward to deal with two-way THz spectral data of unknown mixtures for spectral resolution of single species. SMCR requires pure variables which have intensity contributions from only one component for extracting the content information. However, for the spectra of many materials in THz region (about 0.1–3 THz), pure variables are usually unavailable for the overlap of absorption peaks or the presence of baseline. To settle this problem, inverted second derivative was employed as an intermediate step to optimize the determination of pure variable. To test the effect, the proposed method was performed on simulated and experimental THz spectra of multicomponent systems. It is demonstrated that SIMPLISMA combined with inverted second derivative spectra is a promising tool to deconvolve multicomponent systems contributing to the identification of ingredients in unknown mixture in THz region.