Tannin is a polyphenolic compound widely present in plants and has strong astringent and oxidative properties. The following is a common method for determining tannin content:
principle
The determination of tannin content is to measure the absorbance of the blue-black compound generated by the interaction of tannin and iron ions at a certain wavelength, and then calculate the tannin content in the sample through the standard curve.
Instruments and Reagents
Ethanol: Use ethanol with a purity of 95% or more.
Acetone: Use acetone with a purity of 95% or better.
Iron chloride: Use dry iron chloride to make a 10 mmol/L iron ion solution.
Phenanthroline: make 1% phenanthroline solution.
Acidic Buffer: Use a buffer with a pH of 2.5.
Cuvette: A certain quality cuvette can be obtained through washing, drying and weighing.
UV-Vis Spectrophotometer or Colorimeter.
Steps
Sample preparation: Take about 1 g of sample, add about 20 mL of ethanol, stir with a magnetic stirrer at room temperature for 30 minutes, then filter with filter paper and collect the filtrate into a 50 mL cuvette.
Add iron ions: Add 1 mL of 10 mmol/L iron ion solution and 1 mL of 1% phenanthroline solution to the cuvette, and stir evenly with a magnetic stirrer.
Add buffer: Add 2 mL of acidic buffer to the cuvette and mix well.
Determination of absorbance: add acetone to the scale line in the cuvette, mix well and use a UV-visible Spectrophotometer or Colorimeter to measure the absorbance of the solution. The tannin content in the sample can be calculated according to the standard curve.
Beichao reminds you: different types of tannins have different absorbances at different wavelengths, so it is necessary to select an appropriate wavelength for measurement and properly control sample pretreatment and correction.
