"The role of solvents in the imbibition of ascorbic acid by zeolites"

Ascorbic acid is commonly used as an antioxidant
agent in form of a powder. This allows the
immediate availability of the molecule but cannot avoid
the rapid inactivation of the excess. Sodium zeolites
have frequently been proposed as agents for the controlled
release of absorbed molecules. In order to prepare
controlled release antioxidant agents, we treated
sodium X and Y zeolites with ascorbic acid dissolved in
organic solvents in order to establish how much acid they
were able to retain and understand the retention and
release mechanism. We found that the acid: (i) undergoes
a dissociation and H+/Na+ exchange with zeolite;
(ii) is retained as sodium salt while the zeolite is protonated;
(iii) is released as a function of the sodium salt
solubility into the solvent used. Thus, the imbibition was
function of the nature of the solvent and, in aqueousorganic
solvent mixtures, it was a direct function of the
water concentration in the range 0–1% and an inverse
function in the range 1–11%. It follows from above that,
when sodium zeolite is used as a support for ascorbic
acid, water percent in the range 0–11% may control the
release as the ascorbate salt into aqueous–organic solvent
mixtures.