Identification of insecticide residues with a conducting-polymer electronic nose

Current methods for the detection and identification of pesticide residues on agricultural and landscape plants require time-consuming and expensive chemical analyses [14]. This problem causes delays for agricultural land managers in making important crop-management and pest-control decisions involving pesticide applications. The presence of pesticide residues on food crops also is a major health concern, especially on fresh fruits and vegetables because of the broad impacts of health laws regulating the safety of plant-related food and fiber products in commercial markets. The inadequacies of current conventional chemical-analysis methods, such as gas chromatography-mass spectroscopy (GCMS) for determining the identities of pre-harvest and postharvest crop residues on the surfaces of plant products, has produced a strong need for new more rapid chemical-detection methods to effectively identify pesticide residues on plants in crop fields and in post-harvest storage facilities prior to plantproduct introductions into commercial markets. Many electronic sensor devices have been evaluated for specific capabilities of detecting insecticides in the environment. Most previous insecticide-detection research has focused on organophosphate (OP) insecticides because this broad class of organic compounds is highly toxic to mammals, as powerful cholinesterase inhibitors (nerve toxins), resulting in significant threats to the health of humans and the environmental due to widespread commercial use of OPinsecticides on agricultural lands [2]. Organothiophosphates (P–S, P=S) are related to phosphoryl-type (P=O) organophosphates that include such lethal nerve and chemical warfare agents as VX, Soman and Sarin. Organophosphate residues on agricultural crops, livestock, and poultry products have the potential to migrate into aquifers and contaminate water resources following direct applications to plants and soils or from accidental spills or leaks from storage tanks and waste repositories. Most OP insecticides are non-persistent, but a few OP-contaminants, such as azinphos methyl, have long half-lives and may persist in the environment for long periods of time (up to four years). Insecticides have been detected using a wide range of techniques, including electrochemical [5-8], luminescent [9-11], fluorescent [12-14], optical [15], polymer [16], hydrogels [17], and surface acoustic wave (SAW) electronic-nose sensors [18,19] as well as immunological (antibody) [20-23], enzyme-linked immunosorbent assay (ELISA) [24], enzymatic biosensor [25], microbial biosensors [26] and fiber optic biosensors [27,28]. Electronic chemical-detection methods are ideally suited for repeated, rapid detections needed for making pesticide-management decisions and for monitoring pesticide levels on crops for regulatory safety enforcements. In particular, portable electronic-nose (e-nose) devices are especially useful for these applications due to the capability of rapid detections, sensor recovery, high reproducibility, accurate determinations, and high sensitivity to polar volatile organic compounds (VOCs) typical of most commercial pesticides. This study is part of a series of efficacy studies to assess the relative suitability and capabilities of e-nose devices to detect agricultural pesticide residues in various commercial plant-production settings. The current paper reports on the development and testing of methods for use with an intrinsically conducting polymer (ICP) e-nose technology to potentially identify insecticide residues on plant surfaces in agricultural fields. The objectives of this study were to 1) Abstract