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 y tterbium bisphthalocyanine Langmuir-Blodgett (LB) films when exposed t o 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 thioca rbamate, respectively) and physical properties (Henry's Law constant, water solubility and octanol/water partitioning coefficient, among oth ers). The present results suggest that the chemical composition determ ines the relative change of the measured properties. On the other hand , the kinetics of the adsorption and desorption processes seem to be c losely related to the hydrophobicity of the pesticides. The developmen t of sensors suitable for monitoring the volatilisation of pesticides at laboratory and field scales is discussed in terms of the difference s observed in the responses to the tested vapours. (C) 1998 Elsevier S cience S.A. All rights reserved.