Effects of temperature and concentration of the accelerators ethoxylated alcohols, diethyl suberate and tributyl phosphate on the mobility of [C-14]2,4-dichlorophenoxy butyric acid in plant cuticles
J. Schonherr et al., Effects of temperature and concentration of the accelerators ethoxylated alcohols, diethyl suberate and tributyl phosphate on the mobility of [C-14]2,4-dichlorophenoxy butyric acid in plant cuticles, PEST MAN SC, 57(1), 2001, pp. 17-24
Intrinsic activities of monodisperse ethoxylated dodecanols (MEDs), diethyl
suberate (DESU) and tributyl phosphate (TBP) were investigated using Steph
anotis floribunda leaf cuticular membranes (CMs) and [C-14]2,4-dichlorophen
oxy butyric acid (2,4-DB) as a model solute. When sorbed in c degrees uticu
lar membranes, MEDs, DESU and TBP increase solute mobility and are called a
ccelerators for this reason. With MEDs, dose-effect curves Clog mobility vs
accelerator concentration) were Linear but, with DESU and TBP, curves conv
ex to the x axes were obtained that approached a maximum at 90 and 150 g kg
(-1), respectively. Accelerators increased the mobility of 2,4-DB in the CM
s by 9- to 48-fold, and effects were larger at lower temperatures (range 15
-30 C). Activation energy for diffusion of 2,4-DB was 105 kJ mol(-1) decrea
sing with increasing accelerator concentrations to 26 kJ mol(-1) with DESU
at 90 g kg(-1) and 64 kJ mol(-1) with TBP at 150 g kg(-1). Thus, the intrin
sic activity of DESU was much higher than that of TBP, which implies that,
for a given effect, less DESU than TBP would be needed. MEDs were also very
effective accelerators, lowering activation energies to 36 kJ mol(-1). Dat
a are discussed in relation to increasing rates of foliar penetration of ac
tive ingredients at low temperatures. (C) 2001 Society of Chemical Industry
.