ATR FT-IR spectroscopic imaging

Kazarian, S.G. and Chan, K.LA. (2006) Application of ATR-FT-IR spectroscopic imaging to biomedical samples. Biochim. Biophys. Acta, 1758, 858-67. 

Observation of a Penetration Depth Gradient in ATR FT-IR Spectroscopic Imaging Applications... 

It was demonstrated that concentration profiles of different components can be obtained utilizing the partial least squares method. With concentration profiles readily measurable, it is possible to obtain other quantities such as diffusion type, that is, Fickian versus non-Fickian mechanism of diffusion. The application of in situ ATR FT-IR spectroscopic imaging has been employed to investigate polymer interdiffusion of PVP and polyfethylene glycol) (PEG) under high pressure CO2 [74]. The diffusion mechanism of the system was described based on the spectroscopic imaging data, and it was found that CO2 molecules dissolved in the polymeric system greatly enhanced the interdiffusion process. 

Kazarian SG, Chan KLA, Tay FH. ATR-FT-IR Imaging for Pharmaceutical and Polymeric Materials From Micro to Macro Approaches. In Salzer R, Siesler HW, editors. Infrared and Raman Spectroscopic Imaging. Germany Wiley-VCH 2009, p 347-375. 

Transmission mode FT-IR imaging of microfluidic devices remains attractive because it is important to be able to spectroscopically access the full flow of the system. Certain flow regimes, droplets in oil for instance, can produce results that are obscured by the ATR approach as the depth of penetration may not reach the aqueous droplet and could instead image only the carrier fluid, providing insufficient information about the desired system. 

This time-resolved measurement method can be applicable to relatively slow transient phenomena, as its time-resolved measurements are undertaken while the movable mirror is at rest. The number of applications of step-scan FT-IR spectrometry to time-resolved measurements currently is more than that by any other method, and it has been applied to various studies in many fields such as studies of biomolecules, liquid crystals, polymers, photochemical reactions in zeolites, oxidation-reduction reactions on electrode surfaces, and excited electronic states of inorganic complexes. Further, this method has been applied to time-resolved measurements in combination with attenuated total reflection (ATR) (see Chapter 13), surface-enhanced infrared absorption (see Section 13.2.2) [10, 11], infrared microscopic measurements (see Chapter 16) [12], and infrared spectroscopic imaging (see Chapter 17) [13]. 

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