Abstract
The characterization of an economic and ease-to-use carbon paste acetylcholinesterase (AChE) based biosensor to determine the concentration of pesticides Paraoxon and Dichlorvos is discussed. AChE hydrolyses acetylthiocholine (ATCh) in thiocoline (TC) and acetic acid (AA). When AChE is immobilized into a paste carbon working electrode kept at +410 mV vs. Ag/AgCl electrode, the enzyme reaction rate using acetylthiocholine chloride (ATCl) as substrate is monitored as a current intensity. Because Paraoxon and Dichlorvos inhibit the AChE reaction, the decrease of the current intensity, at fixed ATCl concentration, is a measure of their concentration. Linear calibration curves for Paraoxon and Dichlorvos determination have been obtained. The detection limits resulted to be 0.86 ppb and 4.2 ppb for Paraoxon and Dichlorvos, respectively, while the extension of the linear range was up 23 ppb for the former pesticide and up to 33 ppb for the latter. Because the inhibited enzyme can be reactivated when immediately treated with an oxime, the biosensor reactivation has been studied when 1,1'-trimethylene bis 4-formylpyridinium bromide dioxime (TMB-4) and pyridine 2-aldoxime methiodide (2-PAM) were used. TMB-4 resulted more effective. The comparison with the behavior of similar AChE based biosensors is also presented.
Highlights
Organophosphorus (OPs) pesticides are very toxic compounds, intensively used in agriculture because of their high insecticidal activity and their rapid mineralization in the environment [1]. Their presence in the environment is very harmful for wildlife and human health as they irreversibly inhibit the catalytic activity of acetylcholinesterase (AChE), an enzyme which catalyzes the hydrolysis of the acetylcholine (ACh), one of the most important neurotransmitters playing a vital role in the central and peripheral nervous system [2,3]
It is observed an exponential increase of the current intensity according to a law of the type: Ið potÞ 1⁄4 Ae pot=B
In this paper we have reported the results of the determination of the concentration of Paraoxon and Dichlorvos by means of an AChE carbon paste biosensors
Summary
Organophosphorus (OPs) pesticides are very toxic compounds, intensively used in agriculture because of their high insecticidal activity and their rapid mineralization in the environment [1] Their presence in the environment is very harmful for wildlife and human health as they irreversibly inhibit the catalytic activity of acetylcholinesterase (AChE), an enzyme which catalyzes the hydrolysis of the acetylcholine (ACh), one of the most important neurotransmitters playing a vital role in the central and peripheral nervous system [2,3]. Cal activity some OPs have been used as Chemical Warfare Agents (CWAs) [5,6] In presence of these health risks, in recent years a growing attention has been paid in developing reliable, fast and inexpensive analytical systems to monitor this family of pesticides. The most critical point in the development of biosensors is the
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