Evaluation of the ambiguity in second-order analytical calibration based on multivariate curve resolution: A tutorial

Abstract

The aims of the present tutorial are the following: (1) to show the importance of applying all the chemically sensible constraints which are necessary to retrieve interpretable component profiles when processing second-order analytical data with multivariate curve resolution – alternating least-squares (MCR-ALS), (2) to demonstrate that the constraints allow one to reduce or even remove the impact of the rotational ambiguity in the MCR-ALS solutions, and (3) to provide details on how to estimate the uncertainty in the predicted analyte concentrations which is derived from any remaining ambiguity with a recently developed N-BANDS method. Both simulated and experimental data sets are examined for this purpose. Recommendations are given for including the ambiguity uncertainty in addition to the statistical reports and analytical figures of merit in every MCR-ALS calibration protocol, to assess the reliability of the analytical results.