Rapid Determination of Total Ester in Chinese Liquor by Coulometric Titration

A method for determination of the total ester in Chinese liquor by coulometric titration was proposed. The platinum electrodes were used as working electrode pairs, with pH composite glass electrode as indicating electrode, and 0.80 mol·L^-1 potassium sulfate solution as supporting electrolyte. H⁺ generated by constant current electrolysis was used to titrate the remaining OH^- in the sample after pretreatment, till to pH 7.70 for titration end-point. The total ester in sample was determined by Faraday's law of electrolysis. As shown by the results, the whole determination process could be completed about 10 min. Test for recovery was made by standard addition method, giving results in the range of 88.0%-106%. The proposed method was applied to determination of the total ester in actual Chinese liquor samples, and there was no significant difference between the determination results by this method and those by potentiometric titration specified in the national standard.