Partition coefficients of salicylic acid between water and the micelles of some non-ionic surfactants

Abstract

Partition coefficients of ionized and unionized salicylic acid molecules between water and the micelles of several non-ionic surfactants have been determined. Those of unionized molecules decreased with decreasing length of the surfactant alkyl chain and with increasing length of the surfactant polyoxyethylene chain. Ionized salicylic acid partitioned to a significant extent only into those surfactants having more than approximately 44 oxyethylene units in their hydrophile. The findings are discussed in terms of their biopharmaceutical significance.