Fourier-transform infrared HPTLC

Note that Jenke " also cites references to the use of other related analytical techniques, including Head-space GC, high performance thin layer chromatography (HPTLC), supercritical fluid chromatography (SFC) /MS, and supercritical fluid chromatography/ Fourier transform infrared spectroscopy (SFC/FTIR). 

Several so-called hyphenated techniques have been developed, where the developed TLC plate is transferred to a modified spectrometer to record in situ the Fourier transform infrared, surface enhanced Raman, or mass spectra of the separated zones. This way more detailed structural information can be obtained to complement the data from densitometric evaluation. A true hyphenation is the direct application of the eluate from a microbore HPLC column onto an HPTLC plate, which is then developed by AMD. 

Direct, in situ HPTLC-FTIR measurement is carried out by diffuse reflectance using a DRIFT (Diffuse Reflection Infrared Fourier Transform Spectroscopy) unit (Fig. 15) (40-45). It is necessary to take account of the fact that at wavelengths where the absorption is large and the refractive index is high, the incident radiation is almost 100% normally reflected at the surface so that there is scarcely any diffuse reflection, which is that part of the reflection that contains the spectral information concerning the sample, in contrast to the normal (Fresnel) reflection. This means that reflectance minima and not the expected reflectance maxima are obtained at wavelengths of strong absorption. With silica gel, the absorption maxima, also known as residual radiation bands, dominate appreciably in the 1300-... 

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