Chromatogram Evaluation, Environmental

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Chromatogram Evaluation

Description

Electronic image acquisition
For electronic image acquisition the camera – like the human eye – captures polychromatic visible light. Under white light illumination it is the light reflected from the layer background. Under long-wavelength UV light (366 nm) it is the light emitted by fluorescent substances. When short-wavelength UV light (254 nm) is used, substances absorbing UV 254 nm appear as dark zones, provided the layer contains a fluorescence indicator (fluorescence quenching). The TLC Visualizer 2 is CAMAG’s imaging and documentation system operated with visionCATS. visionCATS enables an image-based evaluation of chromatograms for quantitative evaluation. The strength of the electronic image acquisition is the overview of the complete chromatogram.

1- Chromatogram under white light; 2- Chromatogram under UV 254 nm; 3- Chromatogram under UV -366  nm

Scanning densitometry
In classical scanning densitometry the tracks of the chromatogram are scanned with monochromatic light in the form of a slit selectable in length and width. The spectral range of the CAMAG TLC Scanner 4 is 190–900 nm. Reflected light is measured either in the absorbance or in the fluorescence mode. From the acquired data quantitative results are computed with high precision and spectral selectivity.
With the TLC Scanner 4 absorption spectra can be recorded. The strengths of classical densitometry as compared with image evaluation are spectral selectivity and the higher precision of quantitative determinations.

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