Effect of Triton X-100 concentration on NAA penetration through the isolated tomato fruit cuticular membrane

The effect of the surfactant Triton X-100 (TX-100) on penetration of 2-(1-naphthyl) acetic acid (NAA, 1 mM NAA in 20 mM citric acid buffer at pH 3.2) through enzymatically isolated tomato (Lycopersicon esculentum Mill.) fruit cuticular membranes (CM) was investigated at concentrations of 0.001-10% (w/v) using an infinite dose diffusion system. This system permits the study of penetration of an active ingredient under steady-state conditions from a donor solution through an interfacing CM into a receiver solution. NAA penetration was related to TX- 100 concentration where increasing concentration up to 0.1% increased NAA flux and permeance, but concentrations > 0.1% decreased both flux and permeance. Sorption of NAA by the CM was independent of TX-100 concentration up to 0.0475%, but decreased with higher concentrations. The decrease in the NAA permeance coefficient at higher surfactant concentrations (> 0.1%) was less than the decrease in the partition coefficient. This finding is interpreted as evidence that the surfactant affected the permeability of the CM resulting in an increase in the diffusion coefficient of NAA and/or decrease in tortuosity of the diffusion path across the CM. (C) 2003 Elsevier Ltd. All rights reserved.