Surface-modified carbon pastes

Also, sodium montmorillonite-modified carbon paste electrode has been used for the determination of trace concentrations of mercury [80]. Hg + was preconcentrated at the electrode, reduced, and then stripped from the electrode surface in the positive potential scan. At a glassy carbon electrode modified with dithizone, mercury has been determined, applying anodic stripping voltammetry [81]. 

Alvarez-Crespo et al. [69] L-Glutamate Chicken bouillon cubes L-Glutamate dehydrogenase/ entrapped in carbon paste NAD+ modified carbon paste electrode/+0.15 V vs. Ag/ AgCl o-Phenylenediamine polymerised on the electrode surface... 

The detailed preparations and experimental conditions will be not reported here, but the electrochemical determinations were performed by using a modified carbon paste (CP) electrode produced by using the modified sifica surface as sensitive species. The main experimental conditions and results are summarized in Figs. 3.11 and 3.12 and Table 3.2. 

Afldiami, A, Soltani-Felehgari, F, Madrakian, T., and Ghaedi, FL (2014) Surface decoration of multi-walled carbon nanotubes modified carbon paste electrode with gold nanoparticles for electro-oxidation and sensitive determination of nitrite. Biosens. Bioelectron.,... 

Thiols can be oxidised at a variety of solid electrodes, such as noble metals, carbon and carbon with chemically modified surfaces. Mefford and Adams found that relatively high voltages, greater than -1-1 V, were required to oxidise GSH and cysteine at glassy carbon electrodes. Chemically modified surfaces can reduce the oxidation potentials required and hopefully increase specificity and sensitivity. Halbert and Baldwin used cyclic voltammetry to study the electrochemistry of cysteine, homocysteine, A -acetylcysteine and GSH at both unmodified and cobalt phthalocyanine-modified carbon paste electrodes. This non-chromatographic technique was used to measure the relatively high concentrations of GSH in whole blood. The electrochemistry of thiols has been reviewed. ... 

Mixtures of conductive particles with an electrode modifier have also been carried out using carbon paste electrodes. A recent example is the incorporation of PVP, which was protonated and exposed to ferrocyanide (113). The PVP-modified carbon paste electrode behaved similarly to a surface-modified electrode. The advantage of such a system is that the surface could be renewed simply by exposing a fresh layer of modified carbon paste by mechanically removing the surface layer. 

Porphyrin-modified electrodes were widely utilized for quantification of low concentrations of metals, pharmaceutical products, and species of environmental and industrial importance in association with flow techniques. This strategy enhances the amperometric response and sensitivity (the capacitive current is virtually reset), while reducing significantly the time necessary for analyses. Flow injection analysis (FIA) has been extensively explored for this purpose and a revision on the application of porphyrins and derivatives was published some years ago [203]. Alternatively, batch injection analysis (BIA) can be an interesting way for fast analyses utilizing a similar mass transport process to the electrode surface [204]. For example, citric acid was electrochemically determined by BIA using cobalt phthalocyanine modified carbon paste electrodes [205]. 

Electrochemical oxidation of thermally denatured single-stranded DNA (ssDNA) was studied on a room temperature ionic liquid N-butylpyridinium hexafluorophosphate (BPPFg) modified carbon paste electrode (IL-CPE) by Sun et al. [27]. The presence of IL layer on the surface of CPE showed the ability of ionic conductivity and cation exchange extraction. 

Another outstanding example of electrochemical detection of short sequences related to the HBV using MB on chitosan-modified CPE was proposed by Mandong et al. [82]. This electrochemical DNA biosensor was based on MB and chitosan-modified carbon paste electrode (CCPE) for short DNA sequences and PCR amplified real samples related to the HBV hybridization detection. DPV was used to investigate the surface coverage and... 

Arguably, carbon paste is the most useful material for laboratory preparation of various electrometric sensors. In the carbon paste electrode configurations, a selective agent (modifier) is commonly incorporated into the surface via the mixtures with graphite powder and a pasting liquid, when one obtains chemically modified carbon paste electrodes, CMCPEs. For many years, most of applications of CMCPEs in electroanalysis fall mainly amongst voltammetric determinations often, in combination with electrochemical stripping analysis (ESA). 

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