Response of a sensor based on ytterbium bisphthalocyanine Langmuir-Blodgett films to selected herbicides

The response of a sensor based on the changes of the conductivity of ytterbium bisphthalocyanine Langmuir-Blodgett (LB) films when exposed to the vapours of three extended pesticides is studied. The herbicides Imazamethabenz-Me, Terbutryn and Tri-allate were selected on the basis of their different chemical group (imidazolinone, triazine and thiocarbamate, respectively) and physical properties (Henry's Law constant, water solubility and octanol/water partitioning coefficient, among others). The present results suggest that the chemical composition determines the relative change of the measured properties. On the other hand, the kinetics of the adsorption and desorption processes seem to be closely related to the hydrophobicity of the pesticides. The development of sensors suitable for monitoring the volatilisation of pesticides at laboratory and field scales is discussed in terms of the differences observed in the responses to the tested vapours. (C) 1998 Elsevier Science S.A. All rights reserved.