Detection video densitometry

Analytical methods based on fluorescence are preferred over absorption for TLC quantiflcation. Fluorescent substances are excited by long-wave UV light (366 nm) the fluorescence emission in the visible region is detected. In this respect classical and video densitometry are comparable. However, video technology lacks the variable-excitation-based selectivity of classical densitometry. For the detection of fluorescent substances the intensity of the emitted fluorescence (/n) is directly proportional to the amount of substance applied. The most serious drawback of fluorescence measurements is the low quantum efficiency of the excitation process. The light intensity available for fluorescence measurements at a given intensity of illumination is, therefore, much smaller than the intensity that, under the... 

The main improvements in quahtative and quantitative detection systems in TLC are centred around the introduction of densitometry. These involve the use of slit scanning densitometers or video or CCD camera (image processing) [130]. 

---