FLOW-INJECTION POTENTIOMETRIC DETERMINATION OF COKE ACIDITY AND ACETIC-ACID CONTENT IN VINEGAR USING AN ANTIMONY ELECTRODE

A flow injection potentiometric procedure is proposed for the determin ation of acidity of several samples using an antimony/antimony oxide e lectrode. The Delta E/pH curve in phosphate buffer solutions in the pH range from 1.58 to 12.00 showed a linear sub-Nernstian behavior with an operational slope S = -42.1 mV/pH(c) and a conditional standard pot ential of 264.8 mV. This flow potentiometric electrode responds linear ly to low acidity variations of dilute acetic acid solutions from 3.16 to 100mM with a slope of 30.1 mV/dec and analytical frequency of 23 r esults/h. Good reproducibility and an average standard deviation of +/ -0.5% was obtained. The application of this sensor for the determinati on of coke acidity and acetic acid in vinegar is reported.