Behaviour of membrane graphite electrodes in potentiometric titration of bases and reducing substances in acetic acid media

Titrations in nonaqueous solvents

“…Formation of an adsorbed layer of acetonitrile molecules on the surface of platinum in acetonitrile solutions affects electrode behavior by preventing solvated inorganic species from reaching the electrode surface (230). Adsorption-polarized electrodes are reported to give sharp end points in precipitation titrations in acetic acid-water and acetone-water mixtures (260), as do membrane graphite electrodes in potentiometric titrations of bases with perchloric acid, and of reducing substances with lead(IV) acetate, in acetic acid (222). Dual reference electrodes are recommended to counter the high resistance of some solvent systems in electrochemical measurements (93).…”

“…Amalgam and glass electrodes gave similar results for free energies of transfer of alkali metal chlorides between water and aqueous ft'rt-butyl alcohol (63). The silver, silver(I) [222] cryptate couple has been investigated as a solvent-independent reference couple, and gave satisfactory results in water, methanol, acetonitrile, dimethylsulfoxide. tetramethylurea, and nitromethane (777).…”

“…A tabulation of polarographic half-wave potentials of inorganic substances in dimethylformamide, along with information on dimethylformamide as a solvent, provides a useful guide to couples of possible analytical utility (128). The charge transfer rate and mechanism of anodic complex formation between mercury and [222] cryptate was investigated in propylene carbonate and in dimethylformamide (240).…”

“…The properties of 2-propanol and iert-butanol as solvents for acid-base systems have been studied (56,167,168), as have the equilibria of hydrochloric and hydrobromic acids in these solvents (765). The basicity of several organomagnesium and organosodium compounds in the presence of hexamethylphosphotriamide or cryptate 222 has been measured in tetrahydrofuran with a hydrogen electrode (60), as has the acidity of several compounds in dimethylsulfoxide (67). In other acid-base studies, 34 nitrogen-containing asphaltenes with a wide range of basicities were titrated in acetophenone and nitrobenzene (70).…”

Potentiometric Back Titration of Isoniazid in Pharmaceutical Dosage Forms Using Copper Based Mercury Film Electrode

“…Since INH is autooxidized in solutions, direct potentiometric titration of INH is difficult. 11 Many potentiometric methods have also been reported for the assay of INH by making use of commercially available ion selective electrodes [19][20][21][22][23] which are either costly or not readily available in the market. Since copper based mercury film electrode (CBMFE) is cost effective, it has been applied as an indicator electrode for the assay of INH, 24 ascorbic acid, [25][26] sulphamethoxazole.…”