Saturated calomel electrode Saturation analysis

The following data were collected for the analysis of fluoride in tap water and in toothpaste, (a) For the analysis of tap water, three 25.0-mL samples were each mixed with 25.0 mL of TISAB, and the potential was measured with an F ISE relative to a saturated calomel electrode. Five 1.00-mL additions of a standard solution of 100.0-ppm F were added to each, measuring the potential following each addition. 

In the common method of electro-gravimetric analysis, a potential slightly in excess of the decomposition potential of the electrolyte under investigation is applied, and the electrolysis allowed to proceed without further attention, except perhaps occasionally to increase the applied potential to keep the current at approximately the same value. This procedure, termed constant-current electrolysis, is (as explained in Section 12.4) of limited value for the separation of mixtures of metallic ions. The separation of the components of a mixture where the decomposition potentials are not widely separated may be effected by the application of controlled cathode potential electrolysis. An auxiliary standard electrode (which may be a saturated calomel electrode with the tip of the salt bridge very close to the cathode or working electrode) is inserted in the... 

Fhe polarographic analysis is obtained at a dropping mciiiiiry electrode with any conventional three-electrode polarograpb cin[)loying a saturated calomel electrode as the rcCercnco. 1 ho checkers added the 0.5-ml. aliquots of the... 

Cao and Zeng [52] used of an oscillopolarographic method for the determination and the electrochemical behavior of omeprazole. Portions of standard omeprazole solution were treated with 1 ml 1 M ammonia/ ammonium chloride at pH 8.9 and the solution was diluted with water to 10 ml. The diluted solution was subjected to single sweep oscillopolaro-graphy with measurement of the derivative reduction peak at —1.105 V versus saturated calomel electrode. The calibration graph was linear from 0.5 to 10 /iM omeprazole with a detection limit of 0.2 fiM. The method was applied to the analysis of omeprazole in capsules with recoveries of 100-118.6% and RSD of 6.78%. The electrochemical behavior of omeprazole at the mercury electrode was also investigated. 

Apparatus Cyclic voltammetry and amperometric current-time curves were obtained with a Pine Instrument Inc., Model RDE4 bipotentiostat and Kipp Zonen BD 91 XYY recorder equipped with a time base module. All measurements were performed in a conventional single-compartment cell with a saturated calomel electrode as the reference electrode and a Pt mesh as the auxiliary electrode at room temperature. Chronoamperometry was made with EG G Princeton Applied Research potentiostat/galvanostat Model 273 equipped with Model 270 Electrochemical Analysis Software. 

Yang studied the anodic voltammetry of dipyridamole at a glassy carbon electrode [59]. Portions of a standard dipyridamole solution were mixed with 10 mM hydrochloric acid for anodic voltammetry, using a glassy carbon working electrode and measurement of the anodic oxidation peak at 0.62 V (versus saturated calomel electrode). The calibration graph was linear from 0.5 to 10 mg/L of dipyridamole, and over 20 foreign species did not interfere. The method was directly applied to the analysis of dipyridamole in tablets and urine, with recoveries of 100.5-101.2% and a relative standard deviation of 1.5-2.2%. 

Fig, 3.14. Schematic diagram of a jacketed glass cell used for sonoleaching and sonoelectro-analysis of lead in cathode ray TV tubes. BDD boron-doped diamond, CRT cathode ray TV tubes, SCE saturated calomel electrode. (Reproduced with permission of the Royal Society of Chemistry.)... 

In the most sensitive eiectroanaiytical methods, exclusively treated within this context, the analyte ion is electrodeposited on an electrode from an electrically conducting sample solution. Current and potential of subsequent redissolution are due to the concentration and the kind of ion to be determined. For thallium, the reversible redox couple TI /TI° at about -0.5 V versus saturated calomel electrode is used (Bellavance and Miller, 1975). Infinite tolerance towards alkali, alkaline earths and halogenides are great merits for the analysis of biological materials. Because of the preconcentration step included, thallium determination is more sensitive than atomic spectrometric methods. For thallium, the multielement capabilities of the method can hardly be used, because lead and frequently cadmium have to be masked with excess of complexants, leaving just Tl in the potential... 

A three-electrode cell is a standard electrochemical analysis tool for characterization of electrode kinetic processes requiring accurate control of electrochemical potential at the WE (Figure 8-5B). The potential at the WE is monitored relative to nonpolarizable RE that is placed close to the WE to keep measured media resistance (impedance) R between the two electrodes as small as possible. The RE has a constant and reproducible potential when no current flows through it. The saturated calomel electrode (SCE) and the silver-silver chloride (Ag/AgCl) are the most common types of RE in aqueous media. Depending on the electrolyte, other types of reference electrode, such as metal/metal oxide pseudo-reference electrodes, can be used. 

All potentials vs. screen-printed Ag/AgCl pseudo-reference, except values marked with asterisk ( ), which are vs. Ag/3M AgCl double-junction reference electrode, and values marked with dagger CfO, which are vs. saturated calomel. Abbreviations CoPC cobalt phthalocyanine, SPCE screen-printed carbon electrode, GOD glucose oxidase, MWCNT multi-walled carbon nanotubes, NAD nicotinamide adenine dinucleotide, PQQ pyrroloquinoline quinone, FIA flow injection analysis. 

The quantitative analysis requires knowledge of the rate(s) of the heterogeneous electrode reaction(s), reagent diffusion coefficients and the transfer coefficient. If the electrode reaction is reversible, most of these parameters can be determined from the CV experiments. The formal reduction potential, differs from the standard potential, °, because the latter is obtained by extrapolation to infinite dilution, while the former refers to the actual experimental conditions of ionic strength and temperature. For a fast, reversible process, E° => j,2 10 mV if the diffusion coefficients of the oxidized and reduced forms are within a factor of two. Potentials are reported relative to some standard electrode, such as ferrocene/ferrocinium ion, saturated calomel, SCE, or Ag/AgCl, and this must be taken into account in comparing results from different sources. 

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