Potentiometric systems

In addition to the immunochromatographic assays, another system used by the Allies during Desert Storm for the detection of biological warfare agents was the Light Addressable Potentiometric System (LAPS) produced by Molecular Devices (Sunnyvale, CA)19. The LAPS detected toxins and... 

The text by Buffle (above) also covers potentiometric systems in which electron... 

Although all potentiometric measurements (except those involving membrane electrodes) ultimately are based on a redox couple, the method can be applied to oxidation-reduction processes, acid-base processes, precipitation processes, and metal ion complexation processes. Measurements that involve a component of a redox couple require that either the oxidized or reduced conjugate of the species to be measured be maintained at a constant and known activity at the electrode. If the goal is to measure the activity of silver ion in a solution, then a silver wire coupled to the appropriate reference electrodes makes an ideal potentiometric system. Likewise, if the goal is to monitor iron(UI) concentrations with a platinum electrode, a known concentration of... 

Potentiometric systems, which are less commonly used, measure changes in electric potential caused by interaction of 02 with the cathode. Appropriate electronic equipment transduces the amperometric output into a voltage, which is amplified and recorded on a conventional strip chart recorder. 

Kubota, L. T, Fernandes, J. C. B., Rover, L., and de Oliveiro Neto, G. Determination of acetylsalicyclic acid by FIA-potentiometric system in drugs after on-line hydrolysis. Talanta 50(3).-661-667,1999. 

Simulaiion l.earri moie about calibration of potentiometric systems... 

Determinations of pKa s and log P s were performed by the Sirius PCA 101 Potentiometric System. All macrolides were soluble in water at pH 6 or lower. An approximately 1 mM solution of each macrolide at a constant ionic strength of 0.167N NaCl was titrated from a low to a hi pH. The acid used was 0.5N HCl, and the base, 0.5N NaOH. The acid and base were standardized to four decimal places using NIST standards. The pKg s and log P s were determined in triplicate under an argon atmosphere at... 

J. Junsomboona and J. Jakmuneea, Determination of chloride in admixtures and aggregates for cement by a simple flow injection potentiometric system, in Journal ofTalanta, Wo. 76, 2008, pp. 365-368. 

The pH of the mobile phase is a major factor in the separation of ionizable compounds. As mentioned earlier, the most widely used model considers the retention factor as an average of and k according to the mole fraction of the neutral and ionic forms. The mole fraction depends on p Ta and pH of mobile phase. The pH of the mobile phase is taken to be the same as that of the aqueous fraction and this implies a false assumption. Even when pH is measured after mixing the buffer with the organic modifier, the potentiometric system, calibrated with aqueous standards, does not measure the true pH of the mobile phase. 

The hydrogen concentration cells described above cannot be used at temperatures above 300 °C because Teflon loses its thermal stability. However, a flow-through potentiometric system can be used [13,... 

As shown above, potentials of several electrodes can be simultaneously acquired. Figure 5.26 shows a potentiometric system with eight high-impedance inputs allowing up to eight selective electrodes and a reference electrode to be connected. The impedance adapter board is connected to an A/D converter that is in mrn interfaced to a computer via its serial port. 

Multiplexed 8-channel potentiometric system. (For color version of this figure, the reader is referred to the online version of this book.)... 

The circuit shown in Eigure 5.26 uses this type of board. The board on the left is a potentiometric system that affords connection of up to eight selective electrodes and a reference one. Each electrode is furnished with an impedance adapter the output of which is connected to the multiplexer input of the Ibercomp A/D board—the one under the impedance adapter. The A/D board is connected to the RS485 communication interface, which is equipped with two small transformers. In addition, the A/D board accommodates the RS232C interface, which allows direct connection of the multiplexed potentiometer to the computer. 

It should be mentioned that, if the high-temperature thermodynamic properties (the standard Gibbs energies and the activity/fugacity coefficients) are available for all species of an electrochemical reaction, both E and E can be calculated theoretically and compared with observed potentiometric data. In this way the reUability of an experimental potentiometric system can be confirmed. 

Parra, A., M. Ramon, J. Alonso, S. G. Lemos, E. C. Vieira, and A. R. A. Nogueira. 2005. Flow injection potentiometric system for the simultaneous determination of inositol phosphates and phosphate Phosphorus nutritional evaluation on seeds and grains. J. Agric. Food Chem. 53 7644-7648. 

Marques, I. D. H. C., E. T. A. Marques, A. C. Silva, W. M. Ledingham, E. H. M. Melo, V. L. da Silva, and J. L. Lima Filho. 1994. Ascorbic acid determination in biological fluids using ascorbate oxidase immobilized on alkylamine glass beads in a flow injection potentiometric system. Appl. Biochem. Biotechnol. 44 81-89. 

Guerreiro, J. R. L., A. H. Kamel, and M. G. F. Sales. 2010. FIA potentiometric system based on periodate polymeric membrane sensors for the assessment of ascorbic acid in commercial drinks. Food Chem. 120 934-939. 

A.H. Kamel, ETC. Moreira and M.G.F. Sales, Biomimetic sensor potentiometric system for doxycycline antibiotic using a molecularly imprinted polymer as an artificial recognition element. Sensor Lett., 9 (5) 1654-1660, 2011. 

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