Electrochemical sensor for the determination of parathion based on p-tert-butylcalix[6]arene-1,4-crown-4 sol–gel film and its characterization by electrochemical methods
Introduction
Organophosphate pesticides (OPs) have played an important role in increasing agricultural productivity. Because of their high toxicity and widespread uses in agricultural areas, the residues could be left in our environment [1], [2]. For the sake of human health protection and environmental control, it is important to develop a rapid, selective and sensitive method for the detection of organophosphorous pesticides in water, plants, soils and foodstuff, etc.
Several sophisticated analytical methods based on gas or liquid chromatography coupled with various detections [3], [4], [5], [6], mass spectrometry [7], and thermospray–mass spectrometry [8] for the determination of OPs have been developed. Direct electrochemical methods for the detection of electroactive OPs compounds or applied electrochemical and gravimetric techniques in conjunction with enzymes have also been reported [9], [10], [11], [12].
Recently, the use of molecularly imprinted polymers (MIPs) as specific preconcentration element or detection platform for OPs has been paid more attentions [13], [14], [15], [16], [17]. Molecular imprinting is a technique for obtaining very selective binding sites in highly cross-linked macroporous polymers. Among the applications proposed, a number of studies have recognized the importance of the selective bonding of organophosphates by molecular imprinting for application in catalysis and sensing [18], [19]. Exciting work on parathion sensor based on molecularly imprinting sol–gel film has recently been published [20]. The role of the functional monomers and their requirements for providing several points of noncovalent interaction were examined. The binding to molecularly imprinted polymers in the gas and liquid phase is compared for the same matrix and template system. The time for saturated adsorption of the parathion on this sensor is 24 h when being incubation in 0.1 mM parathion solution, thus, it is difficult to be utilized in parathion determination.
The application of the sol–gel technique to construct molecularly imprinting film supplies a simple material system for surface coatings, and also provides an efficient way of incorporating organic components into inorganic polymeric films in solutions under mild thermal conditions [21]. Compared with acrylic polymer-based films, the control of the thickness, porosity, and surface area is easier, while the selectivity and diffusion are comparable and even better [20].
In this paper, a parathion sensor based on p-tert-butylcalix[6]-1,4-crown-4 as functional monomer is fabricated by sol–gel method using molecular imprinting technology. A sensitively and selectively electrochemical response has been obtained after incubated the sensors in phosphate buffer solution contain appropriate amount of parathion. This imprinted film sensor provides a reliable means for determination of parathion in real samples. The results were consistent well with that obtained by high performance liquid chromatography.
Section snippets
Instruments and reagents
Electrochemical data were obtained with a three-electrode system using a CHI 660A electrochemical workstation (CH Instruments, Texas, USA). The parathion sensor was used as the working electrode, a platinum wire as the counter electrode and a saturated calomel electrode (SCE) as the reference electrode. Scanning electron micrograph was done with a Hitachi X-650 microscope. HPLC system consisted of a LC-10AD model pump (Shimadzu, Japan), SPD-10AV UV–vis detector, shimpark SBC-ODS analytical
Characterization of the surface morphology of the molecularly imprinted sensor
Scanning electron micrograph was applied to characterize the surface morphology of the parathion molecularly imprinting film coated glassy carbon electrode after being extracted by ethanol. As shown in Fig. 2(a), the electrode is covered with porous reticulations. When magnifies the film 35,000× (Fig. 2(b)), cavities caused by volatilization of the solvents or extraction of parathion are observed clearly. These cavities can selectively bind with the object molecular, parathion, and allow them
Conclusion
In conclusion, a sensitive and selective parathion sensor has been fabricated by sol–gel method using molecular imprinted technology. A fast response has been obtained by incubation of the sensor in a parathion solution. The electrochemical behavior of parathion on this molecularly imprinted sensor has been investigated using various electrochemical technologies including voltammetry, chronoamperometry and alternating current impedance spectroscopy. It suggested that the electrode reaction
Acknowledgements
The authors gratefully acknowledge the financial support from the National Nature Science Foundation of China (Nos. 60171023 and 30370397).
Chunya Li received his MS degree in electroanalysis from Wuhan University, China, in 2002. Since 2002, he has been a PhD student in Department of Chemistry at Wuhan University, China. His work focuses on the sensing materials and chemical sensors.
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Chunya Li received his MS degree in electroanalysis from Wuhan University, China, in 2002. Since 2002, he has been a PhD student in Department of Chemistry at Wuhan University, China. His work focuses on the sensing materials and chemical sensors.
Changfa Wang received his MS degree in electroanalysis from Wuhan University, China, in 1986. He is currently an associate professor at the department of Wuhan University, China. He has performed research on chemically modified electrode and their applications in electroanalysis.
Bing Guan received his MS degree in macromolecule from Wuhan University, China, in 2002. Since 2002, he has been a PhD student in department of chemistry at Wuhan University, China. His work focuses on the synthesis of calixarenes.
Yangyang Zhang will receive her BS degree from the Department of Chemistry in Wuhan University, China in 2005.
Shengshui Hu, professor of the Department of Chemistry, Wuhan University, China. From 1988 to 1990, he had been a guest research fellow in Chalmers University, Sweden. In 1995, he worked as a senior visiting scholar in Universitá Degli Studi di Firenze, Italy. During 1995–1998, he was a visiting research fellow in Case Western Reserve University, USA.