Carbon paste electroactive

In recent years, the electrodes of similar structure have also found application in the electroanalytical chemistry, for purposes of researching the electrochemical behavior of solid substances, etc. These electrodes are known as the modified carbon paste electrodes or carbon paste electroactive electrodes [2]. 

Two main types of matrices are described for the design of the sensors a PYC based matrix [21,35] and a carbon paste based matrix [22-31, 33-52], A special design was adopted for the construction of the imprinted polymers based sensors [53]. The most reproducible design was proved to be the one based on a carbon paste matrix. The non-reproducibility of PVC-based matrices is due to non-uniformity and non-reproducibility of the repartition of the electroactive material in the matrix [2],... 

Paste electrodes - electrodes prepared by making a paste from an electron-nconducting material and a binder. The binder may be an electrolyte solution or inert oils like - Nujol. Paste electrodes can be part of batteries [i], where the electroactive material is used to prepare the paste, often with the addition of an inert electron conductor. In - electroanalytical chemistry, unmodified and modified - carbon paste electrodes are used. 

Enzyme sensors can measure analytes that are the substrates of enzymatic reactions. Thermometric sensors can measure the heat produced by the enzyme reaction [31], while optical or electrochemical transducers measure a product produced or cofactor consumed in the reaction. For example, several urea sensors are based on the hydrolysis of urea by urease producing ammonia, which can be detected by an ammonium ion-selective ISE or ISFET [48] or a conductometric device [49]. Amperometric enzyme sensors are based on the measurement of an electroactive product or cofactor [50] an example is the glucose oxidase-based sensor for glucose, the most commercially successful biosensor. Enzymes are incorporated in amperometric sensors in functionalised monolayers [51], entrapped in polymers [52], carbon pastes [53] or zeolites [54]. Other catalytic biological systems such as micro-organisms, abzymes, organelles and tissue slices have also been combined with electrochemical transducers. 

Researchers turned their attention to applications of silica gel as a new electrode material. Silica gel, which has a three-dimensional structure with high specific surface area and is electroinactive in an aqueous medimn can be used as a support for electroactive species during their formation and/or enzymes by adsorption or entrapment [92,93]. Patel et al. recently reported application of poljwinyl ferrocene immobilized on silica gel particles to construct glucose sensors. Efficiency of carbon paste electrodes prepared with these polymeric electron mediators and GOx was comparable to electrodes constructed with other ferrocene based polymeric electron transfer systems. The fact that 70% of initial anodic current was retained after a month when electrodes were kept in the buffer at room temperature shows that polymerization of monomer vinylferrocene in the pores of silica gel and entrapping GOx in the matrix of poljwinyl ferrocene appears to have added stability to the sensors [94]. 

A carbon paste electrode modified with Cu -doped clinoptilolite powder has been evaluated as an amperometric sensor for non-electroactive in flow injection analyses [48]. The conductivity of heulandite single crystals parallel to [100] has been studied under isothermal conditions as a function of the H2O content, small polar organic molecule concentration, and charge compensating cations. Results indicate that heulandite electrodes will be applicable for analytical purposes in aqueous solution [49]. 

In recent work, this same research group has reported on the use of modified carbon paste electrodes for the discrimination of vegetable oils [51]. The oils were used as an electroactive binder material of carbon paste electrodes and the responses of these electrodes immersed in various solutions were used to discriminate the oils. The polyphenol content of olive oil allows it to be differentiated from sunflower or corn oils. In addition, the voltammograms are influenced by the pH and the nature of the ions present, resulting in characteristic signals for PCA even olive oils of different quality (extra virgin, virgin, lampante, and refined) could be discriminated. 

In electrochemistry an electrode is an electronic conductor in contact with an ionic conductor. The electronic conductor can be a metal, or a semiconductor, or a mixed electronic and ionic conductor. The ionic conductor is usually an electrolyte solution however, solid electrolytes and ionic melts can be used as well. The term electrode is also used in a technical sense, meaning the electronic conductor only. If not specified otherwise, this meaning of the term electrode is the subject of the present chapter. In the simplest case the electrode is a metallic conductor immersed in an electrolyte solution. At the surface of the electrode, dissolved electroactive ions change their charges by exchanging one or more electrons with the conductor. In this electrochemical reaction both the reduced and oxidized ions remain in solution, while the conductor is chemically inert and serves only as a source and sink of electrons. The technical term electrode usually also includes all mechanical parts supporting the conductor (e.g., a rotating disk electrode or a static mercury drop electrode). Furthermore, it includes all chemical and physical modifications of the conductor, or its surface (e.g., a mercury film electrode, an enzyme electrode, and a carbon paste electrode). However, this term does not cover the electrolyte solution and the ionic part of a double layer at the electrode/solution interface. Ion-selective electrodes, which are used in potentiometry, will not be considered in this chapter. Theoretical and practical aspects of electrodes are covered in various books and reviews [1-9]. 

Halogenated hydrocarbon [CCI4, CHBrj, C 2HgBr] (l,f) II heterogeneous CP) Electroactive carbon paste, reactive h-CPE) C(R)PE... 

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