Electrochemical Methods for Assessment of Polytrauma Outcomes

In this work we used electrochemical methods, open circuit potential (OCP) measurement with platinum electrode, and cyclic voltammetry (CV) in blood serum to assess redox states in patients with polytrauma (n=56) that allow to evaluate probability of survival early on, and therefore have the potential to improve therapy outcomes. Electrochemical assessment of redox states in sera samples correlated with traditional methods of prooxidant/antioxidant balance quantification. OCP and quantity of electricity passed (Q), calculated from CVs, were significantly different between the survivors and non-survivors. Patients with Q>22 μC (day 1) and OCP>34 mV (day 3) had low chance of survival.     

Prototypical Nonelectrochemical Method for Surface Regeneration of an Integrated Electrode in a PDMS Microfluidic Chip

Abstract

A prototypical method for surface regeneration of an integrated electrode in a microfluidic chip is demonstrated. A platinum wire as working electrode was mounted in a polydimethylsiloxane chip vertical to the chip through the channel. The regeneration of the electrode was easily achieved by drawing the platinum wire out for 5 mm, because the area exposed to the channel or the stream would be altered. With continuous motion, the wire electrode can maintain a fresh surface just like a dropping mercury electrode. The current–time curve and open circuit potential (OCP) of dopamine solution show the performance of this prototypical system.     

Electrochemical Behavior and Determination of Hyoscine‐N‐Butylbromide from Pharmaceutical Preparations

The electrooxidation of hyoscine N‐butylbromide (HBB) was investigated by rotating disk electrode voltammetry, cyclic voltammetry and controlled potential coulometry in 0.1 M HNO₃ and in 0.1 M tetrabutylammonium perchlorate (TBAP) solutions of acetonitrile at a platinum (Pt) electrode. Based on the results obtained, it is suggested that a bromide ion of HBB was oxidized in one reversible step in aqueous solutions and in two reversible steps in acetonitrile. A differential pulse voltammetric (DPV) method at a Pt electrode was developed for the determination of HBB in the concentration range of 1.0 × 10^?6‐1.0 × 10^?3 M. The procedure was applied to the determination of HBB in its formulations as well as its recovery from blood serum and urine samples.     

Variations of the charge and open-circuit potential during the ion adsorption with the formation of irreversibly adsorbed atoms

The transients of the current and open-circuit potential (OCP) for the B^z± ± ze → B_ad process, where B_ad is an irreversibly adsorbed atom, are described analytically. The analysis is based on the earlier obtained relationships for variations in the total charge and OCP of a hydrogen electrode during the irreversible adsorption of neutral species. A graphic method of estimating the OCP shifts and integral current transients (E^ads = const) corresponding to various surface coverages with B_ad is proposed. Dedicated to the ninetieth anniversary of Ya.M. Kolotyrkin’s birth.     

Variations in the Charge and Open-Circuit Potential of a Platinum Electrode during Adsorption of Iodine and Iodide Ions

The adsorption of iodine and iodide anions on a Pt/Pt electrode (0.5 M H₂SO₄ as a supporting solution) is compared using potentiodynamic and galvanostatic charging curves, transients of the current and open-circuit potential (OCP), and analytical measurements. Variations in the charge and OCP during the adsorption obey relationships derived for strong adsorption of neutral species and ions on a hydrogen electrode with the formation of irreversibly adsorbed atoms. The main product of the I₂ and I^– chemisorption in acid solutions is adsorbed iodine atoms. However, adsorption of iodine occurs in noticeable amounts and above a monolayer in the form of species that undergo electrodesorption during a cathodic polarization to potentials of the beginning of hydrogen adsorption. In the presence of a monolayer of adsorbed iodine atoms, potential of the zero total charge of a Pt/Pt electrode is in the oxygen adsorption region.     

Study on the Impedance Characteristic and Electrocatalytic Activity of Platinum‐Modified Polyaniline Film

The composite electrode of platinum‐modified polyaniline film is formed in 0.5 M H₂SO₄ + 3 mM H₂PtCl₆ solution by cyclic potential or constant potential deposition of platinum particles in polyaniline film. To make a comparison, the polyaniline film with the same initial thickness and structure is also treated with the cyclic potential or constant potential polarization in 0.5 M H₂SO₄ solution. The electrochemical impedance spectroscopy (EIS) of the composite electrode of platinum‐modified polyaniline film is studied in sulfuric acid solution and compared with the EIS of the polyaniline film without platinum dispersion. The results show that the different modes of potential polarization affect greatly the nature and distribution of the platinum particles, instead of the structure of the polyaniline film (matrix). The electrode reaction kinetics and mass transport process parameters involving charge transfer resistance (R_ct), double layer capacitance (C_dl), constant phase elements (CPE) and Warburg impedance in platinum substrate/platinum‐modified polyaniline film/solution interface are discussed on the basis of the interpretation of the characteristic impedance spectra and connected to the electrocatalytic activity on the oxidation of methanol molecules.     

Ta2O5 templated growth of droplet-like platinum particles by potentiodynamic polarization of tantalum in aqueous solution of hexachloroplatinic acid

By potentiodynamic polarization of mechanically polished tantalum in a diluted aqueous solution of hexachloroplatinic acid, droplet-like platinum microparticles were electrodeposited, embedded into the simultaneously formed Ta₂O₅ film. The roughness factor of platinum of 31 was achieved. Within the potential region of both hydrogen and oxygen underpotential deposition, in both acidic and alkaline solutions, the composite Pt/Ta₂O₅ electrode displayed an excellent electrochemical response characteristic of smooth polycrystalline platinum. The preparation method applied in this work presents an easy way to obtain an electrode surface combining the behaviour of smooth polycrystalline platinum with the behaviour of microdisc arrays. Its electrocatalytic effectiveness was demonstrated for an oxygen reduction reaction in alkaline solutions.     

The potential dependence and kinetics of HCOOH adsorption on rhodium electrodes

The formic acid adsorption on an electrochemically prepared rhodium electrode has been studied by the radiochemical method. Electrochemical properties of the rhodium electrode surface in 0.5 M H₂SO₄ have been investigated by cyclic voltammetry. It has been shown that starting from E=0.20 V the rate of HCOOH adsorption is markedly potential dependent being practically independent of the electrode potential up to E=0.20 V. It seems that the HCOOH adsorption process may be explained on the basis of the two-sites kinetics model. The data obtained for HCOOH adsorption on a rhodium electrode have been compared with those for a platinum electrode reported previously.     

Vibrational Spectra of the Molten Nitrate/Platinum Electrode Interfacial Region

Raman spectra and IR reflection-absorption spectra are measured for the interfacial region between a platinum electrode and molten NaNO₃, KNO₃, and binary eutectic LiNO₃–KNO₃. The design of high-temperature spectroelectrochemical cells used in recording vibrational spectra of the region is described. Effects of electrode potential on the NO^- ₃ion inner-vibrational spectra are studied.     

Cathodic polarization behavior of self-supporting polyaniline film electrode

The preparation method of a self-supporting doped-polyaniline film electrode and its open-circuit potential (OCP) in NaClO₄ and Na₂SO₄ solutions with different pH value as well as cathodic polarization behavior have been investigated for the purpose of discussing the corrosion electrochemical behavior of polyaniline (PANI) in the acid solution. X-ray photoelectron spectroscopy (XPS) reveals that the lower pH corresponds to higher doping level of H⁺ in the film and a more positive OCP of PANI film electrode. OCP of the PANI film reached 0.35 V vs. SCE in 1M H₂SO₄, which is more positive than that of most metals, suggests that PANI would act as cathode when it couples with these metals. The cathodic polarization experiments indicate that the dominating cathodic polarization process of PANI is reversible doping and dedoping reaction and the reduction of dissolve oxygen has very little contribution to it. The potentiostatic current-time curves exhibit a large transient current density at initial stage of polarization, which should be attributed to the charge stored in the film and a relative less steady state current density at the subsequent stage of polarization, which is provided by its doping/dedoping equilibrium activity. Such a current characteristic of PANI electrode might be the force of PANI to provide the passivation protection for some active-passive metals. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 10, pp. 1205–1212. The text was submitted by the authors in English.     

Amperometric Sensor and Immobilized Enzyme Electrode for the Determination of Enzymatic Activities

Abstract

A sensitive method for the rapid determination of activities of soluble or immobilized enzymes, based on the electrochemical detection of hydrogen peroxide is described. Kinetic studies (Vmax and K_M determinations) can be performed for all H₂O₂ generating enzymes (i.e. most of the oxidases) using an amperometric probe with a platinum anode at a fixed potential.

When associated with an immobilized glucose oxidase membrane, this sensor constitutes a glucose electrode and the activity of any hydrolase which releases glucose can be measured. There is no need for other auxiliary enzymes and no preincubation step is required. The possibility to carry out continuous analysis constitutes the main advantage of the described method.     

The GC determination of cisplatin as platinum(II) from pharmaceutical preparations and blood sample of cancer patients

Summary A capillary gas chromatographic method is described for the determination of cisplatin based on the complexation of platinum(II) with bis(isovalerylacetone) ethylenediimine (H₂IVA₂en) and extraction in chloroform. The chromatography was carried out on a BP1 or a BP5 column with an FID. Copper(II), nickel (II) and palladium(II) separated completely and did not affect the determination of platinum(II). The method was applied of the determination of cisplatin in a pharmaceutical preparation and blood samples of cancer patients after infusion of cisplatin. The amounts of cisplatin in blood were found to be within 246–283 ng mL⁻¹ with a C.V. of 2.35–4.26%.     

Influence of the cathodic polarization on the stability of Ti surface in concentrated KOH solutions

The stability of spontaneous thin layers and thin layers formed upon cathodical polarization of Ti in KOH solutions have been studied by potentiostatic and ellipsometric methods. At open circuit potential (OCP) the strongly adherent films, whose thickness depends on the concentration of the KOH solution, were formed. During the cathodic polarization the transformation of these films to weakly adsorbed precipitated layers on the electrode surface was observed. Comparing the theoretically computed curves with the experimental Ψ vs Δ loci measured ellipsometrically, the complex indices of refraction and the thickness of the generated films, from 3.6 to 60 nm in 1 M KOH and from 36 to 105 nm in 5 M KOH (adherent to the electrode surface), were determined. At OCP the rate of film growth increases with increasing the concentration of KOH solution. Cathodic polarizations change the chemical composition and retard the rate of film growth. Based on the ellipsometric and electrochemical data the chemical compositions of the formed films consisted of TiO₂, Ti₂O₃, TiO₂·H₂O, Ti(OH)₃ and TiOOH·nH₂O.     

Electrochemical quartz crystal microbalance analysis of the cathodic process in a lithium-ion battery

The surface processes at carbon and platinum electrodes have been studied using the electrochemical quartz crystal microbalance technique in organic electrolyte solutions for lithium ion batteries. The changes in resonance frequency were analyzed as a function of the electrode potential, indicating that the process depended not only on the electrode material but also on the cathode potential. In the solution containing LiBF₄ as the electrolyte, the main product at the platinum surface was Li₂CO₃ and LiF, whereas formation of lithium alkylcarbonates was the primary process at the platinum and carbon electrodes in LiPF₆ solution.     

Electrode Potentials of Cells with an Electrolyte Based on Zirconium Dioxide in Gas Mixtures N2+ O2+ CO2+ CO: A Platinum Electrode

Steady-state potentials of various platinum electrodes are measured in cells containing electrolyte ZrO₂+ Y₂O₃(10 mol %) in the temperature range 673–773 K in binary equilibrium gas mixtures N₂+ O₂and CO + CO₂, as well as in four-component nonequilibrium gas mixtures N₂+ O₂+ CO₂+ CO containing 0–3 vol % CO and 0–10 vol % O₂. Adding CO to a gas mixture makes the electrode potential deviate from equilibrium, which is explained by chemisorption of CO on the electrode. The oxygen, which is adsorbed on platinum, interacts with CO; as a result, CO₂undergoes desorption and the surface concentration of CO drops.     

Pt掺杂对Mo-Ru-Se簇合物电催化氧还原性能的影响

直接甲醇燃料电池(DMFC)是理想的移动电源,但因金属Pt阴极催化剂的选择性较差,甲醇在阴极产生“混合电位”,导致电池效率降低。抗甲醇氧电还原催化剂可降低“混合电位”,是解决该问题的有效的方法。     

Response to high acidity and basicity at a platinum electrode in chronopotentiometry

A simple and rapid method is developed to determine the high acidity and the basicity of solutions by chronopotentiometry with a platinum working electrode. The acidity range from 5.0 mol/l H⁺ to 1.0 mol/l OH⁻ can be measured by the adjustment of deposition potential and time. The response mechanism to acidity and basicity has been explored. The transition potential plateau in chronopotentiograms is caused from the oxidation of hydrogen adsorbed on electrode surface.     

Electrochemical detection of glucose from whole blood using paper-based microfluidic devices

Electrochemical paper-based analytical devices (ePADs) with integrated plasma isolation for determination of glucose from whole blood samples have been developed. A dumbbell shaped ePAD containing two blood separation zones (VF2 membranes) with a middle detection zone was fabricated using the wax dipping method. The dumbbell shaped device was designed to separate plasma while generating homogeneous flow to the middle detection zone of the ePAD. The proposed ePADs work with whole blood samples with 24–60% hematocrit without dilution, and the plasma was completely separated within 4 min. Glucose in isolated plasma separated was detected using glucose oxidase immobilized on the middle of the paper device. The hydrogen peroxide generated from the reaction between glucose and the enzyme pass through to a Prussian blue modified screen printed electrode (PB-SPEs). The currents measured using chronoamperometry at the optimal detection potential for H₂O₂ (−0.1 V versus Ag/AgCl reference electrode) were proportional to glucose concentrations in the whole blood. The linear range for glucose assay was in the range 0–33.1 mM (r² = 0.987). The coefficients of variation (CVs) of currents were 6.5%, 9.0% and 8.0% when assay whole blood sample containing glucose concentration at 3.4, 6.3, and 15.6 mM, respectively. Because each sample displayed intra-individual variation of electrochemical signal, glucose assay in whole blood samples were measured using the standard addition method. Results demonstrate that the ePAD glucose assay was not significantly different from the spectrophotometric method (p = 0.376, paired sample t-test, n = 10).     

Serum organochlorine pesticide and polychlorinated biphenyl levels measured in delivering women from different locations in Tunisia

Blood serum concentrations of polychlorinated biphenyls (PCB) and organochlorine pesticides (OCP) such as dichlorodiphenytrichloroethane and its metabolites (DDTs), hexachlorobenzene (HCB) and hexachlorocyclohexane isomers (HCHs) were measured in maternal serum (n = 82) from mothers living in different regions in Tunisia. Gas chromatography with electron capture detection was used to quantify residue levels on a volume basis of the organochlorine compounds (OCs). The pattern of OCP in human serum showed that DDTs was consistently the prevalent OC in blood. p,p′-DDE, the major metabolite of p,p′DDT, and HCB were found in all serum samples with mean concentrations of 1.69 and 0.42 ng mL^?1, respectively. PCB congeners 138, 153 and 180 were the predominant congeners measured in all serum samples with a detection frequency of 80%, 72% and 83%, respectively. In general, results found in the investigated group are lower than the concentrations measured in serum blood in other countries.