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Metformin‐selective PVC membrane electrode based on metforminium phosphomolybdate ion pair
Author(s) -
Rizk Mahmoud S.
Publication year - 1994
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.280610110
Subject(s) - potentiometric titration , electrode , calibration curve , analytical chemistry (journal) , ion selective electrode , chemistry , isothermal process , standard electrode potential , membrane , titration , ion , reference electrode , selectivity , standard hydrogen electrode , inorganic chemistry , chromatography , electrochemistry , detection limit , thermodynamics , catalysis , organic chemistry , biochemistry , physics
The (1:1) (phosphomolybdate:metformin) ion pair is used as the ion exchanger in preparing conventional plastic membrane electrodes for metformin (Mf) and its performance characteristics were studied. The electrode exhibited a linear response with a good Nernstian slope over a relatively wide concentration range. The calibration graph slope was constant at 57 mV per concentration decade at 25°C for up to 5 days with continuous soaking. Then the slope decreased as the time of soaking increased, reaching 42 mV decade −1 after 20 days. The changes in pH did not affect the electrode performance within the range 3.0–10.5. The standard electrode potentials were determined at different temperatures and were used to calculate the isothermal coefficient of the electrode (0.000695 V °C −1 ). The electrode showed a very good selectivity for Mf with respect to a large number of inorganic and organic cations. The standard addition method and potentiometric titration were used to determine Mf in pure solutions and in pharmaceutical preparations.