Thin Layer Chromatography - Scanning Densitometry 1
In situ scanning of TLC plates employing optical instrumentation has been extensively developed over the past decade and is now considered essential for both the accurate identification of the spot position and the precise quantitative estimation of its content. In most instruments, the plate surface can be examined employing either reflected light, transmitted light or fluorescent light. In addition the incident light may be adsorbed, diffusely scattered, or transmitted through the plate. The normal procedure is to measure the light scattered, reflected or generated by fluorescence from the spot and compare it electronically with light from a part of the plate where no sample has passed (e.g. the channel between the spots). Single beam and double beam instruments are available and both forms are diagrammatically depicted in figure 19.