pH-Switchable vitamin B9 gels for stoichiometry-controlled spherical co-crystallization.

Vitamin B9 gels were found to be pH-switchable by adding triethylamine or acetic acid. Such recyclable gels can be used as novel co-crystallization media, resulting in four stoichiometric vitamin C co-crystals. Under highly supersaturated conditions, uniform microspheres of (VC)·(NA) with different particle sizes were obtained through a spherical crystallization process.