Two-Dimensional Correlation Analysis and Waterfall Plots for Detecting Positional Fluctuations of Spectral Changes
Abstract:In this study, we demonstrate the potentials and pitfalls of using various waterfall plots, such as conventional waterfall plots, two-dimensional (2D) gradient maps, moving window two-dimensional analysis (MW2D), perturbation-correlation moving window two-dimensional analysis (PCMW2D), and moving window principal component analysis twodimensional correlation analysis (MWPCA2D), in the detection of the existence of band position shifts. Waterfall plots of the simulated spectral datasets are compared with conventional 2D correlation spectra. Different waterfall plots give different features in differentiating the behaviors of frequency shift versus two overlapped bands. Two-dimensional correlation spectra clearly show the very characteristic cluster pattern for both band position shifts and two overlapped bands. The vivid pattern differences are readily detectable in various waterfalls plots. Various types of waterfall plots of temperature-dependent infrared (IR) spectra of ethylene glycol, which does not have the actual band shift but only two overlapped bands, and of Fourier transform infrared (FT-IR) spectra of 2 wt% acetone in a mixed solvent of CHCl3/CCl4 demonstrate that waterfall plots are not able to unambiguously detect the difference between real band shift and two overlapped bands. Thus, the presence or lack of the asynchronous 2D butterfly pattern seems like the most effective diagnostic tool for band shift detection.
Keywords: 2D GRADIENT MAPPING; 2D-COS; FREQUENCY SHIFTS; MOVING WINDOW 2D CORRELATION ANALYSIS; MOVING WINDOW PRINCIPAL COMPONENT ANALYSIS 2D CORRELATION ANALYSIS; MW2D; MWPCA2D; TWO-DIMENSIONAL CORRELATION SPECTROSCOPY; WATERFALL PLOTS
Document Type: Research Article
Affiliations: 1: Department of Chemistry, and Institute for Molecular Science and Fusion Technology, Kangwon National University, Chunchon 200-701, Korea 2: Department of Chemistry, and Institute for Molecular Science and Fusion Technology, Kangwon National University, Chunchon 200-701, Korea. firstname.lastname@example.org.
Publication date: April 1, 2011
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