Abstract
The affinities of eight kinds of carbamate pesticides, MIPC, BPMC, PHC, MTMC, XMC, MPMC, MCC and NAC, with bovine serum albumin, BSA, were examined, and their transport behavior was investigated with BSA as a carrier through a liquid membrane system consisting of a hexane source phase (I), a BSA sulution phase (1/15 phosphate buffer) and a hexane receiving phase (II). All these pesticides showed affinity toward BSA, suggesting involvement of the -NHCOO- group in their binding to BSA. The ratio of the BSA-binding form/free-form was high for MCC and XMC, and relatively lower for the others. An inverse correlation was observed between this ratio and the partition coefficient in a water/n-octanol system. The rate constant of pesticide transport from the haxane phase (I) to the water phase was defined as k1 and that from the water phase to the haxane phase (II) as k2. Positive correlations were observed between k1 and water/hexane partition coefficient, and inverse correlations were found between k2 and the partition coefficient with and without added BSA. It is thus evident that the transport behavior of carbamate pesticides across a water membrane is governed primarily by partition coefficients between water and the hexane phase and that the addition of BSA accelerates the transport of pesticides in the case of lower partition coefficients. Essentially the same was found for steroidhormones in a previous paper. In the case of a lower partition coefficient, the k1 process is a rate-determining step in the transport system, while the rate-determining is changed to the k2 process with increase of the partition coefficient.
