Cocrystallization as a tool to solve deliquescence issues: The case of l-lactic acid

Out of 32 possible coformers tested, four were found to form cocrystals with l-lactic acid and the crystal structures of 1:1 l-lactic acid:d-tryptophan and 1:1 l-lactic acid:3-nitrobenzamide were determined. The hygroscopic behavior of these latter two was studied and compared to the behavior of pure l-lactic acid. Significant improvement was observed: dynamic vapor sorption at 25 °C revealed that water absorbed at 90% relative humidity dropped from 1.3157 g/gsample to 0.0017 g/gsample or 0.0299 g/gsample, with cocrystals of d-tryptophan and 3-nitrobenzamide respectively. This illustrates the effectiveness of cocrystallization as a tool to treat deliquescent materials.