Employment of multivariate curve resolution to liquid chromatography coupled with NMR

Abstract

NMR spectral data from aliquots at different retention times of an ordinary liquid chromatographic column were resolved into individual concentration and spectral profiles using multivariate curve resolution based on alternative least squares (MCR-ALS) and canonical correlation analysis (CCA). Samples were a number of the reaction product mixtures obtained at different experimental conditions, based on a simple experimental design, and for synthesis of α-amido phosphonate. NMR data from different experiments were augmented and aligned using correlation optimized warping (COW) procedure. Orthogonal projection approach (OPA) was applied to make initial estimates for MCR-ALS. CCA was implemented in three steps; the first step was determining the regions of NMR peak clusters, the second was the rank analysis of each peak cluster, and the third was assignment of peak clusters to different compounds using CCA. Employing both resolution methods, the NMR data from liquid chromatographic column was successfully resolved to spectral and concentration profiles of pure components. From the resolved concentration profiles the optimum experimental conditions with maximum yield of reaction were obtained as air atmosphere and at 25 °C. Due to the fact that there is rotational ambiguity in the obtained results of MCR-ALS, the resolved concentration profiles from the two methods were different. However, both methods resulted in the same optimal experimental conditions.