ABSTRACT
40Partition characteristics of 4-(l,l,3,3-tetramethyl) butylphenol (OP) condensed with 3 (OP + 3EO), 5 (OP + 5EO), 9.5 (OP + 9.5EO), 12.5 (OP + 12.5EO), 16 (OP + 16EO), and 40 (OP + 40EO) mol ethylene oxide (EO) between water (pH 5.8) and cuticles isolated from mature tomato (Lycopersicon esculentum Mill. cv. Sprinter) and green pepper (Capsicum annuum L.) fruit were established at 25°C. Partition coefficients (K) were determined for both cuticular membranes (CM) and dewaxed CM (DCM). OP + 3EO sorption by CM and OP + 5EO sorption by CM and DCM increased up to 432 hr. Sorption equilibrium for OP + 3EO by DCM and for the other surfactants by CM and DCM was reached in approximately 24 hr. K values were, in general, inversely related to EO content, ranging from approximately 300 to less than 10. Effects of eight polyethoxy derivatives of OP surfactant (0.1%, w/v) on apparent partition coefficients (K pH) for 2-(l-naphthyl)acetic acid (NAA) between buffer (pH 3.2) and cuticles (CM and DCM) isolated from green pepper fruit and Ficus elastica Roxb. cv. Decora leaves were determined after 48 hr at 25°C. In the presence of surfactant, K pH values for NAA decreased (compared to no surfactant controls) with decreasing EO content, except where OP + 5EO and OP + 7.5EO caused a dramatic increase in NAA sorption by CM. Selected polyethoxy derivatives of linear primary alcohols (0.1%, w/v) were used to further investigate surfactant effects on NAA sorption. While holding hydrophobe chain length constant (C9) and varying EO content (2 to 12 EO), K pH values decreased, in general, with decreasing EO chain length. K pH values decreased with increasing hydrophobe length (C9 to C15) when the EO chain length was held constant at 8. There was no effect of surfactant (C9 + 4EO, C9+ 12EO) concentration on NAA sorption by tomato fruit CM below the critical micelle concentration (CMC), while K pH values were inversely related to surfactant concentration above the CMC. Our data suggest that direct surfactant/cuticle interactions occur and these may have important practical applications in the formulation and performance of agrochemicals.
