Application of carbon fibre microelectrode for studying the impact of pesticides on a frog's egg

With the use of Differential Pulse Voltammetry (DPV), the carbon fibre microelectrode (30 micron diameter) encapsulated in a glass capillary with a 0.5 mm length exposed to solution was investigated as a tool to probe the entrance of electrochemically active pesticides into the frog's fertilized egg so as to study the baseline contamination and to assess the impact of environmental pollutants in water under changing environmental conditions. Frog's egg is a suitable biological system as its development from a single cell occurs in the natural environment with direct exposure to pesticides discharged to water bodies by human activities. Common pesticides such as parathion methyl, parathion ethyl, azinphos methyl and coumaphos were investigated using a carbon fibre microelectrode with optimized DPV conditions as follows: scan rate, 40 m V/s; pulse width, 12.5 ms, pulse amplitude, 100 ms and scan increment, 4 mV. Satisfactory results for the analytical performance were obtained showing detection limits at ppb range, good repeatability (RSD < 7%) and working ranges covering concentrations over three orders of magnitude for the pesticides studied. Results on the effect of various environmental conditions such as temperature, pollutants concentration and exposure time showed biological variation in the response of the frog's egg to pesticide exposure and its suitability as an effective biological indicator to provide a continuous in situ assessment of the environmental impact of pesticides. (C) 1999 Elsevier Science Ltd. All rights reserved.