Poly glassy carbon

A flow injection optical fibre biosensor for choline was also developed55. Choline oxidase (ChOX) was immobilized by physical entrapment in a photo-cross-linkable poly(vinyl alcohol) polymer (PVA-SbQ) after adsorption on weak anion-exchanger beads (DEAE-Sepharose). In this way, the sensing layer was directly created at the surface of the working glassy carbon electrode. The optimization of the reaction conditions and of the physicochemical parameters influencing the FIA biosensor response allows the measurement of choline concentration with a detection limit of 10 pmol. The DEAE-based system also exhibited a good operational stability since 160 repeated measurements of 3 nmol of choline could be performed with a variation coefficient of 4.5%. 

J. Li, L.T. Xiao, G.M. Zeng, G.H. Huang, G.L. Shen, and R.Q. Yu, Amperometric immunosensor based on polypyrrole/poly(m-phenylenediamine) multilayer on glassy carbon electrode for cytokinin N6-(D2-isopentenyl) adenosine assay. Anal. Biochem. 321, 89—95 (2003). 

A large number of examples of redox polyelectrolyte monolayers have been reported [42[. Anson described the adsorption of poly(acrylic acid) onto glassy carbon with electrostatic binding of Ru(NH3)6 and Co(NH3)6 ions from solution [43]. Finklea [44] adsorbed poly(4-vinyl-I-methyl-pyridinium methylsulfate) on self-assembled mercapto-undecanoic self-assembled monolayer (SAM) on gold electrodes to... 

There are a few reports of poly(naphthalene) thin films. Yoshino and co-workers. used electrochemical polymerization to obtain poly(2,6-naphthalene) film from a solution of naphthalene and nitrobenzene with a composite electrolyte of copper(II) chloride and lithium hexafluoroarsenate. Zotti and co-workers prepared poly( 1,4-naphthalene) film by anionic coupling of naphthalene on. platinum or glassy carbon electrodes with tetrabutylammonium tetrafluoroborate as an electrolyte in anhydrous acetonitrile and 1,2-dichloroethane. Recently, Hara and Toshima prepared a purple-colored poly( 1,4-naphthalene) film by electrochemical polymerization of naphthalene using a mixed electrolyte of aluminum chloride and cuprous chloride. Although the film was contaminated with the electrolyte, the polymer had very high thermal stability (decomposition temperature of 546°C). The only catalyst-free poly(naphthalene) which utilized a unique chemistry, Bergman s cycloaromatization, was obtained by Tour and co-workers recently (vide infra). 

I. 4-methoxyacetophenone (30 //moles) was added as an internal standard. The reaction was stopped after 2 hours by partitioning the mixture between methylene chloride and saturated sodium bicarbonate solution. The aqueous layer was twice extracted with methylene chloride and the extracts combined. The products were analyzed by GC after acetylation with excess 1 1 acetic anhydride/pyridine for 24 hours at room temperature. The oxidations of anisyl alcohol, in the presence of veratryl alcohol or 1,4-dimethoxybenzene, were performed as indicated in Table III and IV in 6 ml of phosphate buffer (pH 3.0). Other conditions were the same as for the oxidation of veratryl alcohol described above. TDCSPPFeCl remaining after the reaction was estimated from its Soret band absorption before and after the reaction. For the decolorization of Poly B-411 (IV) by TDCSPPFeCl and mCPBA, 25 //moles of mCPBA were added to 25 ml 0.05% Poly B-411 containing 0.01 //moles TDCSPPFeCl, 25 //moles of manganese sulfate and 1.5 mmoles of lactic acid buffered at pH 4.5. The decolorization of Poly B-411 was followed by the decrease in absorption at 596 nm. For the electrochemical decolorization of Poly B-411 in the presence of veratryl alcohol, a two-compartment cell was used. A glassy carbon plate was used as the anode, a platinum plate as the auxiliary electrode, and a silver wire as the reference electrode. The potential was controlled at 0.900 V. Poly B-411 (50 ml, 0.005%) in pH 3 buffer was added to the anode compartment and pH 3 buffer was added to the cathode compartment to the same level. The decolorization of Poly B-411 was followed by the change in absorbance at 596 nm and the simultaneous oxidation of veratryl alcohol was followed at 310 nm. The same electrochemical apparatus was used for the decolorization of Poly B-411 adsorbed onto filter paper. Tetrabutylammonium perchlorate (TBAP) was used as supporting electrolyte when methylene chloride was the solvent. 

Poly B-411, a water-soluble, blue dye (IV) has been used as a lignin model by Glenn et al. (18). The dye was deposited onto a piece of filter paper, which was then attached directly to a glassy carbon anode. The anolyte contained 10 mM veratryl alcohol and 0.1 M tetrabutylammonium perchlorate (TBAP) in methylene chloride. The catholyte contained only... 

Fig. 26.2. Amperometric immunosensors set-up using a biotinylated copolymer poly(pyrrole-biotin, pyrrole-lactitob-ionamide) coated platinum or glassy carbon electrodes and three enzymatic markers (GOX-B, PPO-B, HRP-Ab) for the detection of cholera antitoxin. (A) HRP-immunosensor, (B) GOX-B-immunosensor, (C) PPO-B-immunosensor. Mred/Mox = hydroquinone/quinone Gox = biotinylated glucose oxidase PPO — biotinylated polyphenol oxidase HRP-Ab = peroxidase-labeled IgG anti-rabbit antibody.

A tetraruthenated porphyrin was electropolymerised onto glassy carbon and used to catalyse the oxidation of nitrite to nitrate, with the resultant current giving a selective measure of the concentration of nitrite ion [81]. As an alternative method, soluble poly(3-octyl thiophene) [82] was cast along with tridodecylmethylammonium chloride onto glassy carbon, to give electrodes with superior selectivity over PVC-based membranes to lipophilic ions such as bromide or nitrate. 

Glass-like carbons (glassy carbons) are produced by the pyrolysis of different precursors, such as phenol-formaldehyde resin, poly(furfuryl alcohol), cellulose, etc., through an exact control of the heating process [88,89], They are characterized by an amorphous structure and also by... 

Carbon C (electrographite, Acheson graphite) Carbon black-filled polymers, graphite-filled plastics, graphite-felt, glassy carbon (anode only), porous carbon, poly-p-phenylene (synthetic metal)... 

Fig. 2.11. Cyclic voltammograms of a poly(aniline)-coated glassy carbon electrode (deposition charge ISO mC, geometric area 0.38 cm2), recorded at 5 mV s 1 in oxygen-free 0.1 mol dm 3 citrate/phosphate buffer at pH 5 in the absence (—), and in the presence (—), of 1 mmol dm-3 NADH. Before each scan the electrode was held at -0.3 V for 3 min to ensure complete reduction of the film.

Fig. 2.17. Plots of the current at +0.1 V for a poly(aniline)/poly(vinylsulfonate)-coated glassy carbon electrode (deposition charge 150 mC, geometric area 0.38 cm2) rotated at 9 Hz in 0.1 mol dm- 1 citrate/phosphate buffer at pH 7 as a function of the NADH concentration showing the stability of the electrode response. Four replicate calibration curves recorded in succession over 4h using the same electrode are shown ( ) run 1 ( ) run 2 (A) run 3 and (O) run 4. The solid line is drawn as a guide for the eye.

Fig. 2.28. Case diagram for NADH oxidation at a glassy carbon electrode coated with a poly(aniline)/poly(vinylsulfonate) film. The points are the experimental data. The surface and case boundaries have been determined from the inhibited fit parameters given in Table 2.8. The residuals are shown as a function of the concentration of NADH below the plot.

Fig. 2.29. Experimental data from poly(aniline)/poly(vinylsulfonate) film deposited on a glassy carbon electrode (0.38 cm2, Qi — 150 mC). The response to increasing NADH concentration as shown by the points. The lines represent the uninhibited... 

---