A. Chamel et B. Gambonnet, SORPTION AND DIFFUSION OF AN ETHOXYLATED STEARIC ALCOHOL AND AN ETHOXYLATED STEARIC AMINE INTO AND THROUGH ISOLATED PLANT CUTICLES, Chemosphere, 34(8), 1997, pp. 1777-1786
Sorption and transfer of an ethoxylated stearic alcohol and an ethoxyl
ated stearic amine into and through plant cuticles were investigated u
sing enzymatically isolated tomato and pepper fruit cuticles. Sorption
was rapid during the first hour and equilibrium was nearly achieved w
ithin 48 hours for amine and 72 hours for alcohol. Sorption was greate
r for the alcohol and there was a relatively small difference between
the two plant species. Cuticle/water partition coefficients (K-cw) det
ermined at two surfactant concentrations (0.1 and 1 mM) were greater a
t the lower concentration. K values for alcohol were 239 and 205 at 0.
1 mM, and 84 and 88 at 1 mM for tomato and pepper, respectively. Desor
ption of both surfactants from cuticles during washing with water was
very slow and was not complete. After 3 hours washing, 81% and 85% of
amine, and 85% and 87% of alcohol were still retained by tomato and pe
pper fruit cuticles, respectively. Transfer measurements through cutic
les expressed by flux measurements and permeability coefficients (P) s
howed that the surfactant penetration increased linearly in relation t
o lime after a steady state was reached; the linear regression coeffic
ient was generally between 0.98 and 1 for individual measurements. The
transfer was more rapid for alcohol for the three tested concentratio
ns (0.1, 1 and 5 mM). For pepper cuticles, the difference observed bet
ween the two surfactants was greater at the lower concentration. Data
obtained were used to calculate diffusion coefficients (D) both from f
lux measurements and hold-up times. Diffusion was greater for alcohol
which means that this surfactant has a better mobility than amine with
in cuticles. Thus, cuticular permeability to the two surfactants was q
uantitatively analysed with the determination of the three characteris
tic parameters : P, K and D. (C) 1997 Elsevier Science Ltd.