A TRIAZINE HERBICIDE MINISENSOR BASED ON SURFACE-STABILIZED BILAYER-LIPID MEMBRANES

This work describes an electrochemical technique that is suitable for rapid and sensitive screening of the triazine herbicides simazine, atr azine, and propazine. Egg phosphatidylcholine and dipalmitoylphosphati dic acid (DPPA) were used for the formation of self-assembled bilayer lipid membranes supported on silver wire (s-BLMs). Evidence that BLMs could form on silver wires was collected by means of ellipsometry whic h was done to investigate samples consisting of lipids deposited on pl anar reflective silver films. The interactions of triazines with s-BLM s produced electrochemical ion current increases which reproducibly ap peared within similar to 10 s after exposure of the lipid membranes to the herbicides, The sensitivity of the response was maximized by use of BLMs composed of 35% (w/w) DPPA and by alteration of the phase dist ribution within membranes by the introduction of 1.0 mM calcium ions i n bulk solution. The mechanism of signal generation could be a result of rapid adsorption of the triazine on the surface of s-BLMs with a co nsequent rapid reorganization of the electrostatics of the membrane, T he magnitude of the current signal was linearly related to the herbici de concentration, which could be determined at the nanomolar level, Th e present triazine minisensor exhibited good mechanical stability and longevity (routinely over 48 h), reproducible response characteristics (i.e., sensitivity and response to a given concentration of triazine in solution), fast response times, and low detection limits, The senso r can be simply and reliably fabricated at low cost, Studies have show n high selectivity for triazines in the presence of insecticides and p esticides.