ABSTRACT
Many soft drinks contain vitamin C (ascorbic acid). Vitamin C is included as not only nutrient factor but also an antioxidant for drinks. There are iodine titration method and indophenol method for analysis of vitamin C, this report introduces indophenol method.
Firstly, acidify the sample with mixed solution of metaphosphoric acid and acetic acid. After that, titrate with indophenol standard solution. The endpoint of the titration is detected as color change from colorless to red-purple with photometric probe.
Measurement procedure
| 3.1. Factor measurement for indophenol standard solution | |
| (1) | Take 1 mL of standard solution into 100 ml tall-beaker with volumetric pipet. |
| (2) | Add 60 mL of additive solvent. |
| (3) | Immerse the probe and start titration with indophenol standard solution. |
| 3.2. Measurement of vitamin C in sample | |
| (1) | Take 2 mL of sample into 100 ml tall-beaker with volumetric pipet. |
| (2) | Add 60 mL of additive solvent. |
| (3) | Immerse the probe and start titration with indophenol standard solution. |
Vitamin C, also known as ascorbic acid, is an essential nutrient that plays a crucial role in maintaining overall health. It is commonly found in various fruits and vegetables, and its presence in commercial products, such as soft drinks, is of interest for quality control and nutritional analysis. In this article, we will explore the process of measuring vitamin C content in soft drinks using the indophenol method and an Autotitrator COM-A19.
- Indophenol Method: The indophenol method is a widely used technique for determining the vitamin C content in samples. It involves the reaction between ascorbic acid and 2,6-dichloroindophenol, resulting in the formation of a blue-colored compound. The intensity of the blue color is proportional to the vitamin C concentration and can be measured spectrophotometrically.
- Autotitrator COM-A19: The Autotitrator COM-A19 is a sophisticated instrument that automates the titration process, providing accurate and precise results. It offers precise control over reagent addition and endpoint determination, making it suitable for complex analyses like the determination of vitamin C content.
Procedure:
Step 1: Preparation of Reagents:
- Prepare a 0.1% (w/v) solution of 2,6-dichloroindophenol in distilled water.
- Prepare a standardized solution of ascorbic acid of known concentration (usually 0.1% w/v).
Step 2: Calibration:
- Calibrate the Autotitrator COM-A19 using the standardized ascorbic acid solution. Follow the manufacturer’s instructions for calibration procedures.
Step 3: Sample Preparation:
- Take a measured volume of the soft drink sample (e.g., 10 mL) and transfer it to a suitable container.
- If the sample contains pulp or solids, filter it to obtain a clear liquid for analysis.
Step 4: Titration:
- Place the container with the soft drink sample on the Autotitrator COM-A19.
- Set the titration parameters on the instrument, including titrant volume, stirring speed, and endpoint determination method.
- Initiate the titration process, allowing the Autotitrator COM-A19 to add the 2,6-dichloroindophenol reagent to the sample.
- The Autotitrator COM-A19 will continue adding the reagent until the endpoint is reached, as determined by the color change from colorless to a persistent light pink or until a pre-set equivalence point is achieved.
Step 5: Calculation of Vitamin C Content:
- Based on the volume of the standardized ascorbic acid solution used for calibration and the volume of soft drink sample titrated, calculate the vitamin C content in the sample.
- Express the vitamin C content in milligrams per liter (mg/L) or any other suitable unit.
The measurement of vitamin C content in soft drinks is essential for quality control and nutritional analysis. The indophenol method combined with the automation provided by the Autotitrator COM-A19 offers a reliable and efficient approach for determining the vitamin C concentration in soft drink samples. This analysis can aid in evaluating the nutritional value and compliance of soft drinks with regulatory standards. Proper calibration, accurate sample preparation, and adherence to the instrument’s instructions are crucial for obtaining precise and reliable results.