The invention provides methods, apparatus, and systems for performing high-throughput preparation and screening of salts and polymorphs of drug candidates. The invention is directed towards enhancing the pre-formulation discovery process used for drug development. In particular, processes that determine suitable salts and processes that discover substantially every polymorph that can form from a particular drug candidate are provided. The processes are performed using several apparatuses that are specifically configured to carry-out various steps in a high-throughput characterization process. One such apparatus is configured for synthesizing a plurality of library members based on, for example, a library model generated by a computer system. Another apparatus may filter the synthesized solution to provide a substantially pure mixture that can be subjected to salt or polymorph testing. Yet another apparatus may be used to crystallize mixtures on a substrate such that the crystallized mixture can be screened by one or more screening devices.