A solution can be made in a solvent other than the eluent. However, in order to avoid a different local migration of the sample, it is necessary to dry the plate before eluting.
If the product absorbs under UV, it is sufficient, before elution, to check under a UV lamp whether or not a deposit is observed. If this is not the case, the solution deposited is then too low in concentration.
As a general rule, the mixture to be analyzed, the starting reagents, the pure products if they are commercial and the co-deposits (analysis mixture + reagents or commercial products) are deposited.
This phenomenon can be due to the presence of chemical functions establishing strong hydrogen bonds with silica. The compounds then tend to trail on the stationary phase, the spot losing its disc shape and becoming very elongated; the determination of a frontal ratio is then very difficult.