Nickel-chromium electrode as a detector in flow-injection amperometry: Determination of glycerol

A flow-injection amperometric method for glycerol determination in samples relevant to the industrial production of soaps, detergents and such is pres ented. A nickel-chromium alloy micro-cylindric electrode was used as the el ectrochemical detector, which after a pretreatment exhibited good repeatabi lity and stability. The method involved glycerol oxidation by an inactive N i(OH)(2) surface film to a Ni(III) layer, usually described as NiOOH (forme d in the range from 0.40 to 0.50 V vs. Ag/AgCl), and reduction back to the starting hydroxide. The influence of sodium hydroxide (0.1 - 1.0 mol l(-1)) and potassium chloride (0.5 - 3.0 mol l(-1)) concentrations and sample-inj ected volume (10 - 100 ml) on the linear dynamic range, stability and respo nse time of the electrode were evaluated. The proposed system handles about 60 samples per hour and is very stable and suitable for industrial control . Results within 20 and 80%(w/v) glycerol are precise (rsd <2%) and in agre ement with the conventional procedures.