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High tension electrical injuries have a high morbidity and mortality. Carbon fibre and graphite used in the manufacture of fishing rods gives them superconductor qualities. We report a case which teaches an important lesson not only in the management of such severe injuries, but also in their prevention.
Graphitized carbon columns (GCC) for high-performance liquid chromatography are relatively new and have a unique ability to resolve isomeric and closely related compounds. The retention mechanism of carbohydrates on GCC is mainly based on adsorption and the flat surface of GCC packings brings about unique selectivity, but also includes hydrophobic interactions. The chromatographic behaviour of monosaccharides, disaccharides, cyclodextrins (CDs), branched CDs, oligosaccharide alditols, chito-oligosaccharides, N-linked oligosaccharides and glycopeptides has been studied, and it has become apparent that the elution patterns are based on the size and planarity of the molecule (position and configuration of linkage).
This study compared the moduli of elasticity of three provisional crown and fixed partial denture resins. Eighteen specimens of each resin were reinforced with carbon graphite fibers and 18 resin specimens from each group contained no fibers. Six specimens of each resin, with and without fibers, were tested within 6 hours of fabrication, after 30 days, and after 60 days of water storage. The mean moduli of elasticity of all the resins increased significantly with fiber incorporation. Water storage did not have a significant effect on the moduli of elasticity of the resins tested.
Selective and sensitive devices for the monitoring of phenol and phenolic compounds are required in clinical and environmental analysis. This paper describes a biosensor for the analysis of phenolic compounds in a flow injection system. The enzyme electrode is based on the use of immobilized tyrosinase and the amperometric detection of the enzymatic product at -50 mV vs. SCE. The enzyme is covalently immobilized on the surface of a carbodiimide-activated graphite electrode. The biosensor responds to a variety of phenolic substrates with different conversion efficiencies. The detection limit for phenol is 0.003 microM (S/N = 3), a quantification limit of 0.01 microM (rsd 3.7%), and an extended dynamic range up to 5 microM is achieved with a sample frequency of 110 samples per hour.
The interaction of cytochrome c with a paraffin-wax-impregnated spectroscopic graphite electrode (WISGE) was studied in a medium consisting of 0.1 M potassium phosphate, pH 7.0, by means of differential pulse and cyclic voltammetry. Ferricytochrome c yields on voltammograms a single cathodic peak C around a potential of -0.3 V (vs. Ag/AgCl) and two anodic peaks AI and AII around the potentials of 0.66 and 0.89 V, respectively. Cathodic peak C corresponds to a catalytic reaction during which ferricytochrome c is reduced to ferrocytochrome c: ferricytochrome c is then regenerated by chemical oxidation of ferrocytochrome c by oxygen adsorbed at the WISGE surface. The first, more negative anodic peak AI corresponds to anodic electrochemical oxidation of tyrosine residues, whereas the second, more positive anodic peak (peak AII) corresponds to an anodic reaction of haemin. Voltammetry at a WISGE may provide a valuable technique for obtaining data about cytochrome c properties on electrically charged surface.
The retention of sixteen monoamine oxidase inhibitory drugs (proparlgylamine derivatives) was determined on a porous graphitized carbon (PGC) column using ethanol-water mixtures as eluents. The HPLC retention characteristics of drugs were correlated with their physicochemical properties using stepwise regression analysis and principal component (PC) analysis. The dimensions of the matrices for PC loadings and variables was reduced using a non-linear mapping technique, varimax rotation and cluster analysis. It has been established that the drugs can be well separated on the PGC column in ethanol-water eluents. Calculations proved that the retention behavior of monoamine oxidase drugs on PGC column is of mixed character: both steric and electronic parameters influence the retention.
Preliminary studies on the properties of a commercially available graphitized carbon black for the solid-phase (or liquid-solid) extraction of drugs and metabolites from biological fluids such as urine and plasma are described. A variety of basic drugs, all of the beta-blocker type, were efficiently extracted from dog plasma and subsequently recovered from the adsorbent using chloroform-methanol mixtures. Similarly metabolites of the non-steroidal anti-flammatory drug ibuprofen also were efficiently extracted from human urine. The proportions of methanol and chloroform used for elution were found to be critical to ensure complete recoveries of adsorbed material. Proton NMR studies of the column eluates from both carbon and C18 bonded silica gel extraction cartridges revealed differences in capacity and selectivity following the application of ibuprofen containing metabolite samples.
The retentions of 45 barbituric acid derivatives were determined on a porous graphitized carbon column (PGC) in unbuffered methanol-water eluent mixtures at various organic phase concentrations and the retention data were correlated with the various hydrophobic and electronic parameters of barbituric acid derivatives. Each derivative showed symmetric peaks in each eluent proving the good separation characteristics of the PGC column without buffering the eluent. Significant linear correlations were found between the logk' value and the concentration of the organic mobile phase in the eluent. Stepwise regression analysis indicated that the retention of barbituric acid derivatives is mainly governed by the electronic parameters, and the lipophilicity of various substituents did not affect significantly the retention, although the eluents were typical reversed-phase eluents.
Stearate-graphite paste electrodes (SGEs) exhibit enhanced dopamine sensitivity and insensivity to asorbic acid electrocatalytic effects in vitro following exposure to unidentified contituents of rat brain tissue homogenates. The present study utilized voltammetry and chronamperometry to compare the electrochemical characteristics of brain-treated SGEs to those treated with potential brain constituent candidates (albumin proteins and phospholipids). Albumin treatments markedly attenuated interference from ascorbate catalytic effects whereas lipids enhanced both electrode capacitance and sensitivity to dopamine. Combined treatments resulted in electrochemical properties that were similar to brain-treated SGEs. Potential mechanisms by which albumin may attenuate ascorbate electrocatalysis of dopamine were investigated using high performance liquid chromatography, with electrochemical detection. The reduction in ascorbate electrocatalytic effects at albumin-treated SGEs may be due to nucleophilic binding of dopamine oxidation products to albumin attached to the electrode surface. Therefore, the unambiguous detection of dopamine by SGEs in vivo may be related to interactions with factors in brain having similar surface-modifying properties.
For an initial study of potentially surface-structural self-organising systems of biological significance by scanning tunnelling microscopy (STM), gramicidin S, a pseudocentrosymmetric cyclodecapeptide with antibiotic properties, was chosen as prototype, recognising its structure as having both intramolecular and intermolecular hydrogen-bond forming propensity. The surface-organised structures, based on gramicidin S hydrochloride deposited on a highly oriented pyrolytic graphite (HOPG) substrate, have been observed by STM in air under ambient conditions. These are characterised in the main by rectangular or rectangle-like structural elements identified with the individual gramicidin S hydrochloride molecules. Two kinds of arrangements of gramicidin S hydrochloride in a two-dimensional array are found, i.e., as a centred rectangular lattice and a primitive rectangular lattice. The STM topographical arrays and the molecular dimensions obtained are in good quantitative agreement with the corresponding X-ray crystallographic data. The differences between the STM results, the theoretical models, and the X-ray crystallographic data are attributed to the intermolecular interactions present in the three-dimensional gramicidin S crystal but absent in the lower dimensional arrays and to the environments in which a gramicidin S hydrochloride molecule finds itself during deposition and drying on the HOPG substrate.
A new glucose biosensor has been fabricated by immobilizing glucose oxidase into a sol-gel composite at the surface of a basal plane pyrolytic graphite (bppg) electrode modified with multiwall carbon nanotube. First, the bppg electrode is subjected to abrasive immobilization of carbon nanotubes by gently rubbing the electrode surface on a filter paper supporting the carbon nanotubes. Second, the electrode surface is covered with a thin film of a sol-gel composite containing encapsulated glucose oxidase. The carbon nanotubes offer excellent electrocatalytic activity toward reduction and oxidation of hydrogen peroxide liberated in the enzymatic reaction between glucose oxidase and glucose, enabling sensitive determination of glucose. The amperometric detection of glucose is carried out at 0.3 V (vs saturated calomel electrode) in 0.05 M phosphate buffer solution (pH 7.4) with linear response range of 0.2-20 mM glucose, sensitivity of 196 nA/mM, and detection limit of 50 microM (S/N=3). The response time of the electrode is < 5s when it is stored dried at 4 degrees C, the sensor showed almost no change in the analytical performance after operation for 3 weeks. The present carbon nanotube sol-gel biocomposite glucose oxidase sensor showed excellent properties for the sensitive determination of glucose with good reproducibility, remarkable stability, and rapid response and in comparison to bulk modified composite biosensors the amounts of enzyme and carbon nanotube needed for electrode fabrication are dramatically decreased.
A biocompatible, nanoporous ZnO film was prepared on graphite electrode by the simple electrodeposition method. Based on the film's strong adsorption ability and friendly microenvironment, it can be used as a good matrix to immobilize myoglobin (Mb) through simple adsorption. Moreover, the entrapped Mb realized direct electron transfer with the electrode and displayed an elegant catalytic activity toward the reduction of hydrogen peroxide, nitrite, and trichloroacetic acid, by which the mediator-free biosensors could be fabricated. Atomic force microscopy, UV-Vis spectra, electrochemical impedance spectroscopy, and cyclic voltammetry, etc. were used to characterize the nanoporous ZnO film and Mb-modified ZnO film. Compared to other methods, electrodeposition of porous material supplied a more simple and convenient approach to prepare biocompatible materials for biosensors.
Kinetics of the surface redox reactions of adriamycin (doxorubicin hydrochloride) adsorbed on paraffin-impregnated graphite electrode (PIGE) and on mercury electrode is measured by square-wave voltammetry. In 0.9 mol/L KNO3 buffered to pH 4.65, the standard electrode reaction rate constants of the first quinone/hydroquinone redox couple (see Scheme 2) on PIGE and mercury are k(s1)=49+/-12 s(-1) and k(s1)=147+/-36 s(-1), respectively. Under the same conditions, the standard rate constant of the second redox couple on the PIGE is smaller than 4 s(-1) and the electron transfer coefficient of the reduction is alpha2=0.35.
The modification of a graphite-epoxy composite electrode (GECE) with bacterial cells along with an analytical application are presented. Pseudomonas putida DSM 50026 was used as a biological component and the measurement was based on the respiratory activity of the cells. The optimization of working conditions of resulting biosensor (including pH and temperature) was conducted and the limit of detection was calculated as 7 microM phenol based on the signal to noise ratio. Then the system was applied for xenobiotic detection. Resulting sample signals were found to be very similar with the standard solutions having the same concentration while the recoveries of the spiked samples were close to 100%.
The electrochemical oxidation of 2'-deoxyadenosine has been investigated in phosphate containing supporting electrolytes in pH range 2-10 at a pyrolytic graphite electrode by cyclic sweep voltammetry, spectral studies, controlled potential electrolysis and related techniques. The oxidation of 2'-deoxyadenosine occurred in a single well-defined oxidation peak (I(a)), over the entire pH range. The electrooxidation occurred by the loss of 6.0+/-0.5 e(-) per mole over the entire pH range. The kinetics of the decay of the UV-absorbing intermediates has been studied and found to follow pseudo first order kinetics having rate constant (k) in the range (5.7-7.7)x10(-4) s(-1). The major products of electrooxidation were separated by HPLC and characterized by GC-MS/MS, (1)H NMR and a tentative mechanism for electrooxidation of 2'-deoxyadenosine has been suggested.
Modified electrodes coated by adsorbed cobalt phthalocyanines are known to show substantial electrocatalytic activity for the electro-oxidation of several thiols in alkaline aqueous solution. In this context, we explore in this study the electrocatalytic activity of adsorbed cobalt phthalocyanine (CoPc) on ordinary pyrolytic graphite electrode for the oxidation of reduced L-glutathione GSH and the reduction of its disulfide GSSG at physiological pH. To do so, cyclic and rotating disk voltammetries were performed and the amperometric results show that a stable electrochemical sensing material, with good reproducibility and sensitivity (in accordance with the concentrations of GSH expected in biological media), can be easily achieved. This opens the way for the design of an electrochemical sensor able to detect these two analytes in biologically relevant experimental conditions (in terms of pH).
With the aim to improve the fibrinolytic properties of carbons by different biological and electrochemical treatments, we modified graphite surfaces by fibrinogen adsorption and subsequent application of various constant potentials before submitting them to plasminogen adsorption. First, we verified that plasminogen (purified or present in human plasma) could adsorb onto these modified surfaces and that adsorbed plasminogen could be converted by t-PA (the principal physiological activator of plasminogen) to adsorbed plasmin. The catalytic properties of the generated enzyme were characterized in assay solutions containing t-PA, fibrinogen and the chromogenic substrate S-2403 (pyroGlu-Phe-Lys-p-nitroaniline, HCl). Experiments showed that the application of electrical potentials to the fibrinogen coating could indirectly affect the properties of the material. In the case of anodic potentials, the amidolytic activity of the generated plasmin was significantly enhanced. Especially, this activity was 10 times higher at a particular potential value.
A novel hemoglobin (Hb)-coated polystyrene (PS) latex bead film was deposited on pyrolytic graphite (PG) electrode surface. In the first step, positively charged Hb molecules in pH 5.0 buffers were adsorbed on the surface of negatively charged, 500 nm diameter PS latex beads bearing sulfate groups by electrostatic interaction. The aqueous dispersion of Hb-coated PS particles was then deposited on the surface of PG electrodes and, after evaporation of the solvent, Hb-PS films were formed. The Hb-PS film electrodes exhibited a pair of well-defined, quasi-reversible cyclic voltammetric (CV) peaks at about -0.36 V vs. SCE in pH 7.0 buffers, characteristic of Hb heme Fe(III)/Fe(II) redox couples. Positions of Soret absorption band of Hb-PS films suggest that Hb retains its near-native structure in the films in its dry form and in solution at medium pH. The Hb in PS films was also acted as a catalyst to catalyze electrochemical reduction of various substrates such as trichloroacetic acid (TCA), nitrite, oxygen and hydrogen peroxide.