IR sampling method

Rather than measure the light transmitted through a sample, as in all of the IR sampling methods discussed thus far, some methods measure the light reflected from a sample. There are various methods employed to measure this reflectance, depending on the properties of the sample. 

It should be mentioned in advance that FT-IR spectrometer is used increasingly in combination with thermogravimetry to identify the released coinxments (solvents or decomposition products) during the heating process. The applicability of some of the IR-sampling methods for the characterization of solid-state forms is discussed in more detail by Threlfall [37] and Bugay [25] and quantitative analysis has been reviewed by Stephenson etal. [38]. 

Two FT-IR sampling methods are commonly employed to measure IR spectra of mixture components separated by thin layer chromatography (TLC). Diffuse reflectance and photoacoustic IR spectroscopy are techniques that can be employed when sample materials are opaque. 

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