In an article published in the peer-reviewed scientific journal Food Additives & Contaminants: Part A, Danish researchers describe migration behavior of the photoinitiator benzophenone (BP) from paperboard, with varying relative humidity. The scientists from the Danish Technical University show that BP migration to the solid food simulant Tenax® increases with increasing humidity. When migration was calculated using common migration models this increase was not found, highlighting the risk of underestimating migration when the relative humidity is not taken into consideration. The authors recommend changing the migration model from a two-layer to a one-layer system, with the latter making more realistic predictions.
The reason for increased BP migration with increasing relative humidity is thought to be related to the molecular scale interaction with paperboard. Paperboard has a total negative surface charge and can adsorb molecules containing aromatic rings, like BP, even though they are not polar. Molecules with low polarity, like BP, compete with highly polar water molecules for adsorption sites on the paperboard. With the presence of more water molecules the less polar BP molecules are displaced and subsequently migrate. The authors speculate that similar phenomena would apply to other typical paperboard migrants with aromatic (sub-)groups, like phthalates. As a consequence migration of widely used printing ink components may be underestimated using the common model.
Barnkob, L. L. and J. H. Petersen (2012). “Effect of relative humidity on the migration of benzophenone from paperboard into the food simulant Tenax® and modelling hereof.” Food Additives & Contaminants: Part A