Part 1: too much time

Plate 1G has been in the chamber for too long. The solvent front should be about 0.5 cm from the top of the plate when you remove the plate from the developing chamber. This ensures maximum separation of the different spots. You can see that the spots are clustered towards the top when you take the plate out too late, making it more difficult to distinguish between spots and impossible to calculate accurate Rf values. Often, students (and the GSI writing up this lab... D: ) will forget about a TLC plate while multi-tasking. Once they remember it, the spots have already run all the way up the plate, and the plate needs to be re-done.

Next time, remember to take your plate out of the developing chamber before the solvent front reaches the top.