Apparatus for holding plates being subjected to multiple development under controlled time

a thin layer plate chromatography apparatus having a container for holding an elution solvent, an open bottom frame for holding one or more plates in the container. The frame has at least one aperture for forcing a drying gas such as nitrogen over the plate. Means for raising and dropping the frame in the container is solenoid operated and a timer is connected to the solenoid so a timed sequence is provided for lowering into the reservoir, removal from the reservoir and drying can be varied according to a preset program. Preferably each subsequent development is slightly larger than the prior development.