DIRECT ELECTROCHEMICAL SENSING OF INSECTICIDES BY BILAYER-LIPID MEMBRANES

This work describes the use of bilayer lipid membranes (BLMs) as sensitive detectors for the direct electrochemical monitoring of the organophosphate and carbamate insecticides monocrotofos and carbofuran, respectively. Egg phosphatidylcholine (PC) and dipalmitoylphosphatidic acid (DPPA) were used for the formation of BLMs. The interactions of monocrotofos and carbofuran with BLMs produced a transient current signal with a duration of seconds, which reproducibly appeared within 3 to 5 min after exposure of the membranes to the insecticides. The sensitivity of response was maximized by use of high concentrations of the charged lipid, and by alteration of the phase distribution within membranes by the introduction of calcium ions in bulk solution. The mechanism of signal generation is related to the absorption of the lipophilic insecticide molecules with a consequent rapid reorganization of the membrane electrostatics. The magnitude of the transient current signal was linearly related to the concentration of monocrotofos or carbofuran in bulk solution with sub-micromolar detection limits.