to determine the concentration of ascorbic acid in fruit juice using DCPIP
To determine the concentration of ascorbic acid in fruit juice using DCPIP (2,6-dichlorophenolindophenol), you can follow the steps mentioned below:
1. Prepare a standard solution: Start by preparing a known concentration of ascorbic acid solution. You can prepare multiple solutions with different concentrations to create a standard curve.
2. Prepare DCPIP solution: Dissolve a known amount of DCPIP in distilled water to create a standardized DCPIP solution. The concentration of DCPIP should be sufficient to react with the expected concentration of ascorbic acid in the fruit juice sample.
3. Set up a control tube: Take a small amount of the standardized DCPIP solution in a test tube. This will serve as a control to measure the initial color of DCPIP.
4. Prepare fruit juice samples: Extract the fruit juice from the fruit of your choice. Make sure to filter the juice to remove any solid particles. Prepare multiple test tubes, each containing a different volume of fruit juice.
5. Mix the fruit juice samples with DCPIP: Add the same volume of standardized DCPIP solution to each test tube containing the fruit juice. It is important to ensure that the volumes of DCPIP and fruit juice are equal in each test tube for accurate comparisons.
6. Observe the color change: The ascorbic acid in the fruit juice will react with DCPIP and reduce it. Initially, the DCPIP solution is blue, but as the ascorbic acid reacts with it, the color changes to colorless. Note the exact point where the color changes for each sample.
7. Measure the absorbance: Using a spectrophotometer, measure the absorbance of each sample at a specific wavelength. The absorbance of the sample is directly proportional to the concentration of ascorbic acid present.
8. Prepare a standard curve: Plot a graph with the concentration of ascorbic acid on the x-axis and the corresponding absorbance values on the y-axis. Use the absorbance values from the standard solutions prepared earlier. From this graph, you can determine the concentration of ascorbic acid in the fruit juice samples by comparing their absorbance values to the standard curve.
9. Calculate the concentration: Determine the concentration of ascorbic acid in each fruit juice sample by using the equation of the standard curve or by interpolation.
By following these steps, you can determine the concentration of ascorbic acid in fruit juice using DCPIP.