Amperometric determination of the water content in acetone, butter and margarine using a wall-tube platinum microelectrode in a flow injection system

Amperometric determinations of the water content in acetone, butter and margarine were performed using a wall-tube platinum microelectrode in combination with a flow injection system. For the butter and margarine samples, acetone containing small amounts of supporting electrolyte was used both as solvent and mobile phase. Linear calibration curves for oxidation of water in acetone were obtained in the range 0.005-0.3% v/v and the limit of detection was determined as 0.003% v/v. The sizes of the currents and the linear range were found to be independent of the supporting electrolyte concentration in the range 1.0 X 10(-4)-2.0 X 10(-3) M, provided that the detection potential was altered to ensure the attainment of steady state currents. The results also indicate that the methanol content in acetone can be determined with the present flow injection system.