This method is suitable for fast detection of total acid in vinegar.
Detection Principle
The main component of vinegar is acetic acid, which contains a small amount of other organic acids. It is titrated with sodium hydroxide standard solution to show the end point with indicator, and the total acid content in the sample is obtained.
Test Material
Droplet containing 0.1moL/L sodium hydroxide standard solution, indicator.
Detection Method
Put 1.0ml of the sample into a 10ml colorimetric tube, add water to the 10.0ml scale, cover and mix well, then put 1.0ml of the sample into another colorimetric tube or test tube, add 4 drops of indicator, titrate with sodium hydroxide standard solution, shake a few times after each drop of solution, and stop titrating until the solution turns purplish red (dark vinegar turns brownish red).A reagent blank test was also performed (1.0mL water was titrated with a standard solution of sodium hydroxide).
Results Analysis
At the same sampling volume, each drop of sodium hydroxide is equivalent to 0.36 g of total acid.The total acid content can be calculated based on the number of drops of the standard solution of sodium oxide used.
Matters Needing Attention
1. Pay attention to the uprightness of the drop bottle when titration to reduce the error.
2. When the result measured by this method differs from the national standard regulation value or the sample label value by only one drop, the presence of field operation error should be taken into account, and the samples failing to meet the standard should be sent to the laboratory for precise quantification.
Reagent quality control
1. The concentration of the standard solution of sodium hydroxide was kept at 0.1008±0.0008moL.
2. The droplet number was maintained at 0.060± 0.002ml/drople