Construction,assessment and applications of a dichromate-selective liquid membrane electrode based on tetrapentylammonium dichromate

A dichromate-selective liquid-membrane electrode based on tetrapentylammonium dichromate dissolved in 2-nitrotoluene is described. The electrode exhibits rapid and linear response to the activity of Cr(VI) anions in the range 5 × 10^?4–2 × 10.2 M dichromate; the slopes of the calibration graphs depend on the acidity. The electrode is useful for end-point indication in titrations of iron(II), arsenic(III), ascorbic acid, thiobarbituric acid, thiourea, and cysteine with dichromate. The electrode is also used as indicator electrode in a potentiometric reaction-rate method for the determination of hydroxyl-containing organic compounds, based on their oxidation by dichromate in acidic solution; ethanol, isopropanol, ethylene glycol, propylene glycol, butylene glycol, and several carbohydrates were determined with a mean error of 1%. The method is applied to determine the ethanol content of alcoholic beverages. Kinetic data are given for the dichromate/ethanol reaction.