**Fourier Transform Infrared and Two-Dimensional Correlation Spectroscopy for Substance Analysis Fourier Transform Infrared and Two-Dimensional Correlation Spectroscopy for Substance Analysis**

Yew-Keong Choong Yew-Keong Choong

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174 Fourier Transforms - High-tech Application and Current Trends

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/66584

### **Abstract**

The development of Fourier transform infrared (FTIR) has had widened its scope of perspective application on different types of substances in terms of technique of material analysis and identification. The tri-step infrared analysis has shown its powerful application in the analysis and interpretation of spectra from pure compound, fraction, raw material, natural product and complex mixture.

**Keywords:** Fourier transform infrared, pure compound, fraction, raw material, natural product, complex mixture

**1. Introduction**

### **1.1. Types of infrared spectrometer: dispersive and Fourier transform**

Dispersive spectrometer has been described as a traditional way in the transformation of Fourier transform infrared (FTIR) spectrometer [1]. The basic function of dispersive spectrometer using diffraction gratings or prisms is to disperse the radiations with wave numbers at several positions. The moving of the gratings is the key that allows the radiations with wave numbers over a short interval of irradiation into the detector. Normally, the spectrum of a sample is created by the ratio between the beam passing through the sample and the reference or background. In comparison, Fourier transform infrared (FTIR) spectrometer is more sensitive and accurate in detecting and determining the higher signal-to-noise ratio within a short period of time. The principle of FTIR is generation of interferogram from the interferometer of the radiation produced by the source. Detecting the signal of radiations with different wave numbers by the Fourier transform to determine frequency domain instead of time domain will enhance the spectrum. In this way, the performance of modern

FTIR is advantageous compared with dispersive spectrometer. FTIR also simplifies the complex algorithm into presentable data and is user-friendly.

The development of numerous sampling accessories, such as attenuated total reflection (ATR), sample cell with different window material for liquid sample, 2DIR sample cell etc., widens the utility of FTIR for multi-sample type analysis. Therefore, the origin of the sample material has no barrier for FTIR, albeit the different objectives of the investigation. In fact, FTIR has been recognised as a rapid, direct and non-destructive analytical method. The challenge confronting FTIR is the interpretation of the qualitative or quantitative spectral data from different direction of view.

Factors that influence the frequency vibration mode of a polyatoms molecule included concentration, thermal, time and chemical reaction. This so-called perturbation is an additional input manipulating the vibration mode of the functional group. Typically dominating the motion of the molecules in the normal mode are only one or few groups which vibrate relatively. The establishment of two dimensional correlation spectroscopy via appropriate perturbation on mid-infrared could be used to enhance the detail of infrared spectrum interpretation.
