Progress in two-dimensional (2D) correlation spectroscopy

The progress made during the last two years in the field of 2D correlation spectroscopy is reviewed. The topics covered by this comprehensive review include the key publications, new concepts and theories of 2D correlation techniques, as well as practical considerations like the effect of peak overlap, band shift, noise, and reference selection. Pertinent activities in other closely related fields, like chemometrics, statistics, and nonlinear optical 2D spectroscopy, are also discussed. Various perturbation methods useful in 2D correlation spectroscopy are examined, including temperature, concentration, mechanical and electrical stimuli, chemical reactions, phase transitions, sorption and diffusion phenomena. Different analytical probes used in 2D correlation are surveyed, such as IR, NIR, Raman, fluorescence, UV–visible, chromatography, NMR, X-ray, and dielectric spectroscopy. Application areas include proteins and peptides, natural and synthetic polymers, liquid crystals, LB films, pharmaceuticals, colloids and solutions, and many more.