The purification of a compound using chromatography is dependent on several factors, including the solubility of the compound, the mobility or flow of the solvent system, and the length of the column or TLC plate. However, it is not typically dependent on the physical state of the pure compound. Here's why :

Option A : The solubility of the compound in the mobile phase and its interaction with the stationary phase are key factors in determining how the compound will migrate in a chromatographic system. Hence, the solubility of the compound does affect its purification.

Option B : The mobility or flow of the solvent system, often referred to as the mobile phase in chromatography, also plays a significant role in the separation of components in the mixture. The rate at which the mobile phase moves can influence how far and how quickly the components of the mixture will travel.

Option C : The physical state (solid, liquid, gas) of the pure compound is usually not a factor in the purification process in chromatography. Whether a compound is solid, liquid, or gas does not typically affect its ability to be separated by chromatography, as it is the interactions between the compound and the stationary/mobile phases that are key.

Option D : The length of the column or TLC plate can impact the degree of separation achieved in chromatography. A longer column or TLC plate can provide more opportunities for the interactions that drive the separation process, often leading to better separation of the components.

So, Option C is correct : The physical state of the pure compound is usually not a factor in its purification by chromatography.