Three-electrode method

The conjugated polymeric liquid crystal, poly(bis(4-methoxy-4 -hexyloxybiphenyl)dipropargylmalonate) (PMHBDPM), can be reversively doped by using electrochemical doping with the common three-electrode method utilizing acetonitrile solution containing tetrabutylammonium fluoroborate (TBAFB) as an electrolyte. 

Fig. 9.10 Schematic representation of the WE polarization curve collected by three-electrode method, illustrating the effect of solid electrolyte reduction [9]. When the applied DC voltage becomes excessively high, the current originating from the progressive increase of local electrolyte nonstoichiometry and/or phase decomposition at the SE membrane surface starts to dominate over the cathodic current...

Danielson, M. J., Analysis of Errors in Using The Two Electrode and Three Electrode Polarisation Resistance Methods In Measuring Corrosion Rates , Corrosion, 36, No. 4, 174-178, April (1980)... 

Bergstrom et al. [63] used HPLC for determination of penicillamine in body fluids. Proteins were precipitated from plasma and hemolyzed blood with trichloroacetic acid and metaphosphoric acid, respectively, and, after centrifugation, the supernatant solution was injected into the HPLC system via a 20-pL loop valve. Urine samples were directly injected after dilution with 0.4 M citric acid. Two columns (5 cm x 0.41 cm and 30 cm x 0.41 cm) packed with Zipax SCX (30 pm) were used as the guard and analytical columns, respectively. The mobile phase (2.5 mL/min) was deoxygenated 0.03 M citric acid-0.01 M Na2HP04 buffer, and use was made of an electrochemical detector equipped with a three-electrode thin-layer cell. The method was selective and sensitive for mercapto-compounds. Recoveries of penicillamine averaged 101% from plasma and 107% from urine, with coefficients of variation equal to 3.68 and 4.25%, respectively. The limits of detection for penicillamine were 0.5 pm and 3 pm in plasma and in urine, respectively. This method is selective and sensitive for sulfhydryl compounds. 

S. Andreescu, L. Barthelmebs, and J.L. Marty, Immobilization of acetylcholinesterase on screen-printed electrodes comparative study between three immobilization methods and applications to the detection of organophosphorus insecticides. Anal. Chim. Acta 464, 171—180 (2002). 

A hanging mercury drop electrodeposition technique has been used [297] for a carbon filament flameless atomic absorption spectrometric method for the determination of copper in seawater. In this method, copper is transferred to the mercury drop in a simple three-electrode cell (including a counterelectrode) by electrolysis for 30 min at -0.35 V versus the SCE. After electrolysis, the drop is rinsed and transferred directly to a prepositioned water-cooled carbon-filament atomiser, and the mercury is volatilised by heating the filament to 425 °C. Copper is then atomised and determined by atomic absorption. The detection limit is 0.2 pg copper per litre simulated seawater. 

This method in some ways resembles the technique for ASV [321,322]. The analytical device is based on a three-electrode system (1) a glassy carbon electrode, which serves as a cathode (2) a saturated calomel electrode (SCE), which is the reference electrode and (3) a platinum counter-electrode during electrolysis. 

A collaborative study conducted by Britton et al. (1984) to determine the most reliable method among the three most commonly used methods (two colorimetric methods and the specific ion electrode method) showed that both pyridine-barbituric acid and pyridine-pyrazolone have similar statistical accuracy. The pyridine-barbituric acid method was preferred by Britton et al. (1984) over the pyridine-pyrazolone method for its convenience (quicker analysis time) rather than the statistical accuracy of data. The electrode method had higher data variability. 

An approach similar to this avoids the use of a comparative nohle metal electrode and neglects overpotential losses at the electrodes. In this method, the potential applied at the hydrogen (or oxygen) electrode (in a three electrode configuration) is compared with the potential generated at an ideal fuel cell anode (or cathode). In the case of a n-type semiconductor photoanode ... 

Recently, Raja et al. [132] proposed a method to calculate efficiency. In this method, the power output by the three-electrode photoelectrochemical cell is calculated by considering the voltage increase between the anode and cathode due to light illumination under external bias conditions. 

A twin electrode thin layer Kissinger cell was designed in which the channel volume could be varied through the use of PTFE spacers [174]. The working and counter electrodes were carbon paste (3.14 m ) and the reference electrode was Ag/AgCl. The performance of the cell was tested on 50 pL portions of chlorpromazine solutions in 0.01 M HCl, and the three cited methods were compared. Linear sweep voltammetry was found to be the simplest to apply and showed moderate sensitivity. 

Voltammetry is the second most utilized technique for electronic tongue devices (see Fig. 2.6). It is a d)mamic electroanalytical method, that is, a current flow passes through the measurement cell (z 0). Voltammetry consists of the measurement of current at a controlled potential constant or, more frequently, varying. In the classic three-electrode cell configuration, the current flows between two electrodes, called working and counter (or auxiliary) respectively, while the potential is controlled between the working and a third electrode, the reference (Kissinger and Heineman, 1996). 

The most convenient and reliable electrical biasing method for use with a hydrated SPE cell has been shown to be a three electrode potentiostatic circuit which maintains the sensing electrode at a predetermined potential vs. a stable reference (1 >3.>j0e The most reversible reference is a Pt/Hp, H+, static or dynamic. In practical instruments, however, good accuracy and convenience are achieved using a large surface area platinoid metal black/air (Op). All work reported in this study utilized the air reference which has a potential of approximately +1.05 V vs. a standard hydrogen electrode (SHE). For convenience, all potentials reported are vs. the SHE ... 

Zinc electrodes for secondary silver-zinc batteries are made by one of three general methods the dry-powder process, the slurry-pasted process, or the electroformed process The active material used in any of the processes for the manufacture of electrodes is a finely divided zinc oxide powder, USP grade 12. 

Voltammetric methods in these methods, a potential is applied to the working electrode using a three-electrode setup (see section 1.6). The electrical current, resulting from charge transfer over the electrode-electrolyte interface, is measured and reveals information about the analyte that takes part in the charge transfer reaction. The potential applied can be constant (chronoamperometry, section2.5), varied linearly (cyclic voltammetry, section 2.3) or varied in other ways (Chapter 2). 

A potentiostatic, three-electrode circuit allows the separation of both functions physically for the reference potential, a non-polarisable electrode is used (a calomel or AglAgCl reference electrode), while the electrical-current conducting electrode is an inert metal electrode. With electrochemical, direct-current methods, the effect of this modification is limited to a reduction of the so-called IR-drop (or ohmic-drop), which is caused by... 

The GECE sensors were used for lead determination in real water samples suspected to be contaminated with lead obtained from water suppliers. The same samples were previously measured by three other methods a potentiometric FIA system with a lead ion-selective-electrode as detector (Pb-ISE) graphite furnace atomic absorption spectrophotometry (AAS) inductively coupled plasma spectroscopy (ICP). The results obtained for lead determination are presented in Table 7.1. The accumulation times are given for each measured sample in the case of DPASV. Calibration plots were used to determine the lead concentration. GEC electrode results were compared with each of the above methods by using paired -Test. The results obtained show that the differences between the results of GECE compared to other methods were not significant. The improvement of the reproducibility of the methods is one of the most important issues in the future research of these materials. 

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