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Determination of α-tocopherol by volumetric or coulometric titration with vanadium(V)

α-Tocopherol-Bestimmung durch volumetrische oder coulometrische Titration mit Vanadium (V)

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Zusammenfassung

Die Oxydation des α-Tocopherols in konz. Essigsäurelösung mit Vanadium (V) wurde zur quantitativen Bestimmung benutzt. Zwei verschiedene Verfahren wurden entwickelt: Im ersten Verfahren wird α-Tocopherol mit Vanadium (V)-Standardlösung mit Hilfe potentiometrischer oder biamperometrischer Indikation titriert. Mengen von 2–20mg wurden mit einer relativen Standardabweichung von 0.3–2.8% und einem relativen Fehler von 1.5% bestimmt; man kann die Titration auch in Äthanol-H2SO4-Lösung durchführen. Bei dem zweiten Verfahren wird Vanadium (V) aus 0.1 M VOSO4-Lösung in Essigsäurelösung elektrolytisch erzeugt und für die Endpunktbestimmung eine modifizierte amperometrische Methode verwendet. Mengen von 0.1–2 mg wurden mit einer relativen Standardabweichung von 0.7–4.3% und einem relativen Fehler von 2.5% bestimmt.

Summary

The oxidation of α-tocopherol in conc. solutions of acetic acid by vanadium(V) has been utilized for its quantitative determination. Two procedures were developed. In the first one α-tocopherol is titrated with a standard vanadium(V) solution applying either potentiometric or biamperometric indicating system. Amounts of 2–20 mg were determined with a relative standard deviation of 0.3–2.8% and a relative error of 1.5%; the titration is feasible also in ethanol-H2SO4 solution. In the second method vanadium(V) is electrogenerated from 0.1 M VOSO4 solution in acetic acid and a modified amperometric procedure for end-point detection is employed. Amounts of 0.1–2 mg of α-tocopherol were titrated with a relative standard deviation of 0.7–4.3% and a relative error of 2.5%.

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Authors and Affiliations

  1. Institute of Analytical Chemistry and Electrochemistry, University of Pisa, Italy

    M. Cospito

  2. Institute of General Chemistry, University of Siena, Italy

    P. Zanello & G. Raspi

Authors
  1. M. Cospito
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  2. P. Zanello
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  3. G. Raspi
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Additional information

We are grateful to the Consiglio Nazionale delle Ricerche of Italy for financial support (contr. n. CT73.01082.03) to one of us (G. R.).

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Cospito, M., Zanello, P. & Raspi, G. Determination of α-tocopherol by volumetric or coulometric titration with vanadium(V). Z. Anal. Chem. 271, 200–203 (1974). https://doi.org/10.1007/BF00430734

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  • DOI: https://doi.org/10.1007/BF00430734

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