Advances in two-dimensional correlation spectroscopy

Abstract Current state of the perturbation-based generalized two-dimensional (2D) correlation spectroscopy is reviewed with the emphasis placed on the advances made since August 1999. This comprehensive review is the third of the consecutive series of reviews since 1993. Major reviews, tutorials, book chapters, a monograph and a journal special issue are discussed first. Recent fundamental and theoretical developments in 2D correlation spectroscopy, e.g., concept of synchronicity and linearity, new computational methods, display and visualization techniques, data normalization, reference spectrum selection, various raw data pre-treatment methods, and post-treatment of 2D spectra, data subdivision, simulation studies, statistical parameters relevant to 2D analysis, new or unusual forms of 2D correlation methods, sample–sample correlation and other chemometrics driven techniques are reviewed. The 2D spectroscopy based on various static perturbations, like temperature, concentration, pressure, position, and other physical variables, applied to different systems, including polymers, biomolecules, solutions, liquid crystals, etc., are examined. 2D correlation spectroscopy relying on transient phenomena, like chemical reactions, diffusion and other relaxation processes, are then studied. Dynamic 2D spectroscopy based on repetitive perturbations, e.g., mechanical, photoacoustic, or electrical stimuli, is also a very active area of research. A number of new types of probes and analytical methods are now incorporated into the field of perturbation-based 2D spectroscopy, including NMR, VCD, fluorescence, and even gel permeation chromatography (GPC) or molecular dynamics calculation. These techniques can be applied by themselves or further combined to provide new opportunities for various 2D hetero-correlation analyses.