I got a single spot of an imine compound and there is no spot for starting materials, but there are some impurities in the base spot in the TLC. I have tried the recrystallization method and still, there are some impurities.
It would really help if you would disclose what compound you are trying to purify and the synthetic method you used.
However, a general method might be to try using preparative reverse-phase chromatography in an organic solvent. This should be much more gentle on your imine. I did a quick Google search and found that there is a Swiss company called, "Zeochem" that sells preparative reverse stationary phases. If you have an HPLC you also have the option to use a preparative reverse-phase column.