A Sample-Sample Correlation Asynchronous Spectroscopic Method Coupled with MCR-ALS to Analyze Challenging Bilinear Data

An approach to construct a secondary asynchronous spectrum via sample–sample correlation (SASS) is proposed to analyze bilinear data from hyphenated spectroscopic experiments. In SASS, bilinear data is used to construct a series of two-dimensional (2D) sample–sample correlation spectra. Then a vertical slice is extracted from each 2D sample–sample correlation spectrum so that a secondary 2D asynchronous spectrum is constructed via these slices. The advantage of SASS is demonstrated by a model system with the following challenging situations: (1) Temporal profiles of different components severely overlap, making spectra of pure components difficult to directly obtain from either original bilinear data or multivariate curve resolution-alternating least squares (MCR-ALS) with non-negativity and unimodality constraints. (2) Every peak in the spectra of the eluted samples contains contributions from at least two components. Hence, two-dimensional correlation spectroscopy (2D-COS) and n-dimensional (nD) asynchr...