| Nicotine, an important alkaloid, is not only the raw material of medicine and chemistry but also the natural pesticide with high performance and low toxicity. Phoxim is one of the organophosphorus pesticides used extensively in agriculture at present. Although belonging to non-permanent materials, they still have some toxicity to men and animals because they may also have a long remanet term in some cases and can accumulate in vivo. Some researches reported that those substances with low toxicity can even lead to cancer and malformation in animals. It is of great significance to enhance the study on determination of toxic substances for keeping ecology balance and safeguarding human health. Novel detection methods-chemical sensors are proposed in view of the defects of determination technologies available. (1) A sensitive nicotine sensor based on molecularly imprinted electropolymer of o-aminophenol is proposed and its configuration and performance are studied in detail. On the condition of weak acidity, the sensitive layer was prepared by electropolymerization of o-aminophenol on a gold electrode in the presence of the template (nicotine). The sensor exhibited good selectivity and sensitivity to the nicotine. The determination limit was 2.0×10-7 mol/L and a linear relationship between the current and concentration was found in the range of 4.0×10-7 ~ 3.3×10-5 mol/L. The sensor has also been applied to the analysis of nicotine in tobacco samples with recovery rates ranging from 99.0% ~ 102%. (2) We studied a new ceria nanoparticles-Nafion film modified sensor for phoxim, which is based on the catalysis of ceria nanoparticles. Phoxim was determined in phosphate buffer solution (pH 7.73) at +0.70 V versus SCE. A linear relationship between the current and concentration was found from calibration curve in the range of 2.0 ~ 102 mg/L. The determination limit was 2.0 mg/L, and the recovery rate was in the range of 101.1% ~ 111.4%. Many nanomaterials are of the unique physical-chemical features and have specific catalytic effect on the electrochemical behave of some materials because of their small size and high surface area-to weight ratio effect. Carbon nanotubes (CNTs) as a nanomaterial with excellent electrochemical performance has been used in chemical and biological sensor design. The major work about CNT in this paper is as follows: (3) Due to excellent film-forming ability and good adhesion of chitosan (CHIT) and the electron conductivity of carbon nanotube, we used them to form a pre-coated CNT/CHIT film on the surface of the glassy carbon electrode (GCE). The plenty amounts of amino groups of CHIT and the strong adsorption of CNT contribute to the formation of a nano-Au layer on the CNT/CHIT surface. By immobilizing HRP through strong electrostatic interaction and adsorption on the surface of nano-Au film, a H2O2 biosensor without electron medium is fabricated. The linear range of detection for H2O2 is from 5.0×10-5 to 2.7×10-3 mol/L. (4) The carbon nanotube treated by microwave plasma chemical modification (MWPCM) was utilized to the fabrication of the glucose biosensor. The treatment process clearly enhances the solubility of carbon nanotube, and the modified carbon nanotube can disperse homogeneously in aqueous solution. The sensing membrane of the biosensor was composed of carbon nanotube, vinylferrocene (VF), bovine serum albumin(BSA) and glucose oxidase (GOD). The sensing parameters and experimental conditions of the biosensors were optimized. The biosensor showed good stability and had a fast response of less than 10 s. The linear range is from 1.2×10-5 mol/L to 7.5×10-3 mol/L with a detection limit of 1.0×10-5 mol/L. The biosensor retained its response after one month storage in the phosphate buffer. |
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