The Impact of Pesticides - Academy Publish

Based on the highly sensitive and selective fluorescence enhancement of watersolubleCdTe/CdS core-shell quantum dots (QD) by organophosphorus pesticides(OPs such as mevinphos, phosalone, methidathion and diazinon), a simple, rapidand selective method using CE with QD/LIF detection (473 nm excitation/532 nmfluorescence) to determine OPs in vegetable samples has been reported (Chen andFung, 2010). The method enables the use of a simple pretreatment procedure basedonly on solvent extraction and eliminates the use of a time-consuming solid phaseextraction step. The CE-QD/LIF method was shown to have a detection limit from50 to 180 μg/kg, working ranges 0.1-30 mg/kg, recoveries 88.7-96.1% andrepeatability (RSD, n=3) 0.36-0.75% for migration time and 2.9-5.7% for peakheight. For tomato samples, the detection limits were more than ten times lower thanmaximum residue levels specified by the Codex Alimentarius Commission for allfour OPs investigated.Real-time detection of an organophosphorus compound using a sol–gel silica planarwaveguide doped with a green fluorescent protein and an organophosphorushydrolase on a yeast-cell surface display was reported ( Enami et al., 2011). Thewaveguide was pumped at 488 nm, and it emitted green fluorescence at the far field.The green fluorescent light at 550 nm changed by 50% from the original power 1min after application of the organophosphorus compound. The results enable thereal-time detection of sarin and other biochemicals by using an in-line fiber sensornetwork.Nanostructured biosensors for the determination of OPs are fabricated by a layer-bylayerassembly technique. In the biosensors, bi-enzymes of acetylcholinesterase(AChE) and choline oxidase (ChOx) are used as biological receptors, while CdTequantum dots (QDs) are explored as fluorescent probes for optical transduction ofthe enzymatic activity. Increasing amounts of OPs lead to a decrease of theenzymatic activity and thus a decrease in the production of hydrogen peroxide,which can quench the fluorescence of the CdTe QDs. The decrease of quenchingrate is relative to the concentration of OPs. Using this biosensor, monitoring of threetypes of commonly used OPs (paraoxon, dichlorvos and parathion) at picomolarlevels is realized. The linear range of detection covers six orders of magnitude (10 −12to 10 −6 M). In addition, the biosensors exhibit a similar limit of detection andcalibration curves for these pesticides, which allow them to be used for the accuratedetermination of total OPs and carbamate content (not the sum of antiacetylcholinesterasetoxicity as obtained by standard cholinesterase inhibition assay)of mixtures of OPs and carbamate pesticides (Zheng et al., 2011].A self-assembled multilayer (SAM) consisting of amino-silanized quartzfunctionalized with gold nanoparticles and coated with indole via a L-cysteine linkerwas reported (Sun et al., 2008). When the SAM sensor was exposed to the pesticide,the indole group of the sensor on the modified film was oxidized to a fluorescentindoxyl group. The oxidation process depended on the pesticide concentration andwas reflected by changes in intensity. The sensor was capable of detectingmethylparathion and monocrotophos in the ppm and ppb range, respectively. Anadvantage of the indole-based SAM sensor is that it could detect OP pesticides inionic and other environmental species, but it was subject to interference at 20equivalents of Fe 3+ ions.AcademyPublish.org - The Impact of Pesticides407