Abstract:
To determine the acid values of tobacco flavors by coulometric titration, the platinum electrode-platinum wire electrode was used as the electrolytic electrode pair, antimony electrode-SCE (saturated calomel electrode) was used as the indicating electrode pair, and 0.5 mol/L potassium chloride solution was used as the electrolyte. The solution was titrated to the pH value of 8.0 by the reaction of electrolytically generated hydroxide ions with free acids in a tobacco flavor sample. Then, the acid value of an experimental tobacco flavor could be calculated by the electrolytic time reached to the titration end point according to Faraday's electrolysis laws, and the spiked recovery experiments were also conducted to validate the method. The results showed that: 1) The recovery range of this method was 96.50%-102.47%, and the relative standard deviations among repeated test results were all less than 1.4%. 2) The acid values of 20 tobacco flavor samples determined by this method showed no significant difference with the potentiometric titration method specified in the tobacco industry standard. 3) The coulometric titration method was suitable for quality control in actual production with convenient operation, less time consuming, and satisfactory precision and accuracy of results.