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ORGANOPHOSPHORUS HYDROLASE-BASED AMPEROMETRIC SENSOR: MODULATION OF SENSITIVITY AND SUBSTRATE SELECTIVITY
Citation:
Chough, S H., A. Mulchandani, P. Mulchandani, W. Chen, J. Wang, AND K R. Rogers. ORGANOPHOSPHORUS HYDROLASE-BASED AMPEROMETRIC SENSOR: MODULATION OF SENSITIVITY AND SUBSTRATE SELECTIVITY. ELECTROANALYSIS 14(4):273-276, (2002).
Impact/Purpose:
The overall objective of this task is to develop scientifically sound sampling and bioanalytical approaches for screening and monitoring of hazardous wastes. These techniques are expected to provide the Agency with improved screening and field portable methods to characterize, reduce, and control risk to human health and the environment. Specific objectives will include development and characterization of the following concepts:
SPMDs for passive accumulation of TICs
Bioassays for toxic and genotoxic compounds
MIPs for volatile and semivolatile toxic organics
Rapid screening assays using the previously listed components.
Description:
The detection of organophosphate (OP) insecticides with nitrophenyl substituents is reported using an enzyme electrode composed of Organophosphorus Hydrolase (OPH) and albumin co-immobilized to a nylon net and attached to a carbon paste electrode. The mechanism for this biosensor involves catalysis of the OP followed by the electrochemical detection of the product, p-nitrophenol. The application of small amounts of mineral oil or silicon oil to the surface of the immobilized enzyme increased the stability and response signals of these sensors. In the case of silicon oil, the response for parathion was five times higher than without oil. In addition, the application of either mineral or silicon oil to the enzyme-coated membranes increased the relative selectivity of the sensor for parathion over paraoxon, most likely reflecting the partition of the substrates between the aqueous and oil phases. The enzyme activity was stabilized for more than two months by the application of either oil to the electrode surface. Compounds evaluated using this technique included parathion, EPN, fenitrothion, and paraoxon. The detection limits for parathion and paraoxon are 15 nM and 20 nM, respectively. These detection limits are substantially lower than those reported for optical assays (e.g., uM range) and lower than those reported using several OPH electrodes (e.g., high nM range). Several characteristics that make this enzyme electrode attractive for further development as a potential field analytical method include; its simplicity and stability, as well as the relatively small amount of enzyme required (i.e., 3 International Units).
The U.S. Environmental Protection Agency (EPA), through its Office of Research and Development (ORD), funded this research. It has been subject to the EPA's peer and administrative review and has been approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation by EPA for use.