FTIR Spectroscopy

  • Thermal transitions
  • Reaction kinetics

A Fourier-transform infrared spectrometer (FT-IR) is an instrument capable of performing rapid, nondestructive mid-infrared (MIR) spectroscopic analysis of samples. An infrared spectrum contains features arising from vibrations of molecular bonds, and the MIR region (400-4000 cm-1) is highly sensitive to the precise sample composition. Data obtained from an FT-IR are absorption spectra that provide information on numerous compounds, including quantitative, qualitative, physical, and chemical information related to individual components. The intensity of absorption is directly proportional to the concentration of the absorbing compound. This is useful for generating standard curves and determining total concentration of the compound of interest, using partial least squares (PLS) techniques. The wavenumber positions of absorbance peaks, peak intensities, and peak widths are useful for functional group and sample identification. Wavenumber positions of absorbance bands are specific to the functional groups in a sample, thus each sample has a unique "fingerprint" absorbance spectrum. Group wavenumbers, or wavenumber regions in which functional groups absorb infrared radiation regardless of other molecular structures, are useful for determining the presence or absence of specific functional groups in a sample. Absorbance peak widths are influenced by the number and strength of functional group interactions with neighboring molecules, and the overlap of functional group absorbance peaks often occurs with increasing the complexity of samples. To facilitate the interpretation of complex spectra, chemometrics approaches are commonly used. Chemometrics algorithms utilize statistical and mathematical techniques to analyze chemical data. Common chemometric approaches include pattern recognition (e.g. hierarchical cluster analysis, principal component analysis, soft independent modeling of class analogies) and multivariate calibration and prediction (e.g. partial least squares, principal components regression). FT-IR instrumentation and multivariate statistical analysis techniques allow for the detection of constituents present in very low concentrations, as well as subtle compositional differences between and among multiconstituent specimens. Discriminant analysis (DA) is used to differentiate between sample types. The FT-IR instrument accessories enable the analysis of solid, powder, viscous, and liquid samples by transmission, ATR, and/or DRIFTS analysis. The FT-IR microscope also enables surface mapping and analysis of smaller samples.

Contact Information

Anton Terekhov, Managing Director of NMR
aterekho@purdue.edu
765-496-9464