Why do we see pteridines but not ommochromes on a TLC plate?
what is the stationary phase? What is the mobile phase?
Ommochromes are not soluble in mobile phase, ( thats all it says in the procedure)
On a thin-layer chromatography (TLC) plate, the separation and visualization of different compounds is based on their relative affinity to the stationary phase (usually silica gel) and the mobile phase (a solvent). Pteridines and ommochromes are two types of pigments found in organisms, but they have different structural and chemical properties that influence their behavior on a TLC plate.
The reason we see pteridines but not ommochromes on a TLC plate lies in their interaction with the stationary phase and the solvent used. Pteridines are typically more polar in nature, meaning they have a higher affinity for the stationary phase, which is usually a polar substance like silica gel. This interaction causes pteridines to be retained longer on the TLC plate.
On the other hand, ommochromes are usually less polar and tend to have a lower affinity for the stationary phase. Consequently, they tend to migrate more with the mobile phase, which is the solvent used in TLC. This behavior results in ommochromes moving faster across the TLC plate compared to pteridines.
To visualize the compounds on a TLC plate, a visualization technique is used. In the case of pteridines, they can often be detected with a UV lamp or by treating the plate with a specific chromogenic reagent that reacts with pteridines, causing them to produce a visible color. This allows us to see and analyze the spots corresponding to the pteridines.
However, ommochromes, being less polar, may not interact strongly with the stationary phase. As a result, they quickly move with the solvent and do not produce well-defined spots on the TLC plate that can be visualized easily, making them difficult to detect using common visualization techniques.
In summary, we see pteridines but not ommochromes on a TLC plate because pteridines have a higher affinity for the stationary phase, resulting in longer retention and better visualization, whereas ommochromes, being less polar, tend to migrate faster with the mobile phase, making them difficult to visualize.