Development of a non-titration potentiometric method for the determination of acidity in vinegar

The acidity of a solution is associated with the concentration of Brønsted acids. This work proposes a new non-titrimetric potentiometric method using citrate buffer for the determination of vinegar acidity. The difference between the pH values before and after the addition of a diluted vinegar sample to 10 mmol L-1 citrate buffer (pH 5.5) was related to the acetic acid concentration. The dynamic range of the quadratic analytical curve was from 3.5 to 20 mmol L-1 (R2 = 0.998). The repeatability was 0.8% for acetic acid at 0.01 mol L-1. Comparison with the conventional titration method showed an error between 0.7% and 4.64% (n = 9) for analysis of commercial vinegar samples The behaviour of the system could be explained using the buffering function.