How do you test for tartaric acid?

Tartaric acid is a four-carbon, dicarboxylic acid that is closely related to succinic acid. One carboxylic acid group is positioned at each end of the molecule, and a hydroxyl (alcohol group) occupies carbons 2 and 3 of the tartaric acid. Tartaric acid can be determined colorimetrically at 520 nm after adding sodium metavanadate plus glacial acetic acid.

Tartaric Acid Standard Solution Preparation

Add 100 mg of reagent-grade tartaric acid to 100-ml volumetric flask containing 80 ml pure distilled water. Mix well to dissolve crystals and add 20 additional ml of water 100 ml mark. Mix well. This standard contains 1 mg/ml of tartaric acid.

Prepare Diluted Quantitative Standards

Place 3.0-, 4.0-, 5.0-, and 6.0-ml portions of the standard tartaric acid solution into separate suitable test tubes or matched cuvettes. Add measured volumes of water to give 10.0 ml solution in each tube. Prepare a blank control tube of 10 ml of water only.

Add Re-agents for Colorimetric Test Reading

To each tube above add 4.0 ml of a freshly prepared 1 in 20 solution of sodium metavanadate plus 1.0 ml of glacial acetic acid. Be sure to take colorimetric readings of each of these solutions within 10 min after the color develops.

Set Colorimeter or Spectrophotometer

Use an instrument that has been warmed up.
Add the water blank cuvette into the instrument.
Set the spectrophotometer to 520 nm, or use a colorimeter with a 520-nm filter.
Obtain a 100 % T; 0.0 absorbance with the water blank tube.

Obtain Tartaric Acid Readings and Prepare Standard Curve

Next, obtain readings of each of the four solutions of tartaric acid.
Use these data to prepare a standard curve by plotting the four absorbances on the ordinate (vertical scale) against the corresponding quantities,of 3, 4, 5 and 6 mg of tartaric acid on the horizontal scale.

Identifying an Unknown Sample of Tartaric Acid

Place the unknown sample at 10 ml volume into the tube and add 4 ml of metavanadate and 1 ml of acetic acid as for standards.
Obtain reading of the solution as before.

Source:

Tartaric Acid, a 4-Carbon, Dicarboxylic Acid with Two Hydroxyl Groups

Tartaric Acid Test Procedure