Reaction rate measurements with fluoride ion-selective membrane electrode. Formation kinetics of ferrous fluoride and aluminum fluoride complexes

Abstract

slowly changing signals. In Table II results are presented for rapidly changing synthetic signals. Resistor R¡ was changed to 15K and integrator times of 50 msec were used for measuring these slopes. Relative errors are again within 0.1% and relative standard deviations are about 0.2%.Results for the determinations of phosphate by the reaction rate procedure are shown in Table III. These results were based on a single phosphate standard. In Table IV results of automatic determinations of glucose in the 5-20 ppm range are presented. In this case adjustments were made to obtain a direct digital readout of the glucose concentration. Rela-tive errors and standard deviations of about 1% were obtained.Many of the rate curves recorded simultaneously indicated that inputs to the rate measuring system were often quite noisy. The results obtained here show the high noise immunity of the integration procedure. In addition, because of its versatility, it is possible to use the same readout system for reactions whose initial rates vary over a wide range, as described in the Instrumentation section.

Flow injection potentiometric determination of Fe(III) using a fluoride-selective electrode as detector

“…If we assume HF and F -to be the predominant fluoride-containing species in FIA experiments their concentrations, with variation in pH, can be calculated from the formation constant of HF. Previous investigation [8] has shown that both species can take part in iron-fluoride complex formation. Also, for the same total fluoride and iron concentrations, the rate of formation of iron-fluoride complex depends on the acidity of the solution.…”

“…Suitability of the FISE for monitoring a reasonably fast reaction of the formation of FeF 2+ in acidic solution has been previously established [8]. Oehme and Dolezalova [9] reported the possibility of direct potentiometric determination of Fe 3+ based on iron-fluoride complex formation but no detailed information was given.…”

“…Since the FISE was developed (1966), the formation constants of many metal fluoro complexes in aqueous solution have been determined. However, there are very few reports in which the FIA determination of metal ions, or their influence on the response characteristics of the fluoride ion-selective electrode, based on metal fluoride complex formation are discussed [4][5][6][7].Suitability of the FISE for monitoring a reasonably fast reaction of the formation of FeF 2+ in acidic solution has been previously established [8]. Oehme and Dolezalova [9] reported the possibility of direct potentiometric determination of Fe 3+ based on iron-fluoride complex formation but no detailed information was given.…”

Estudio de los cambios de la composición química de un ionómero vítreo mediante la técnica de PIXE

“…Esto sugiere que el almacenamiento en medio ácido, favorece la liberación del flúor formando compuestos de calcio y lantano. Existe alguna evidencia de que el aluminio se puede asociar con fluoruro, con el cual, es sabido, que se compleja fuertemente [33]. WILSON [7] postuló la presencia de especies complejas del tipo AlF 2+ y AlF 2 + entre los iones lixiviados de los ionómeros de vidrio.…”

Kinetic Methods of Analysis with Potentiometric and Spectrophotometric Detectors – Our Laboratory Experiences

“…Combination of the simplicity of the kinetic method with the advantages of this sensor (low detection limit, high selectivity) produces an excellent analytical technique for determination of metal ions that form complexes with fluoride. Suitability of the FISE for monitoring a reasonable fast reaction of the formation of FeF 2+ in acidic solution has been established by Srinivasan and Rechnitz [5]. Determination of Fe(III), based on monitoring of the formation of FeF 2+ using FISE is described [6].…”