Separate Lead and Cadmium in a mixture solution by Paper Chromatography.

 

Abstract

This experiment aims to separate the components of a given mixture of inks using paper chromatography. Paper chromatography is a technique used to separate mixtures into their individual components based on their differential migration rates through a stationary phase. In this experiment, we utilize the principles of chromatography to analyze the composition of ink mixtures.

Introduction

Paper chromatography is a widely used method for separating mixtures into their individual components. It relies on the differential affinity of the components for the mobile phase (solvent) and the stationary phase (paper). The components of the mixture are separated as they move at different rates along the paper strip, allowing for visual identification and analysis.

This experiment aims to demonstrate the principle of paper chromatography by separating a given mixture of inks into its constituent components. By comparing the migration distances of the components with known standards, we can identify the individual inks present in the mixture.

Experiment Details

Materials Required:

• Paper chromatography paper
• Given mixture of inks
• Solvent (e.g., water, ethanol)
• Beaker or glass jar
• Pencil or marker
• Ruler
• Watch glass or petri dish
• Developing chamber (optional)

Procedure:

1. Prepare the chromatography paper strip by drawing a horizontal baseline about 1 cm from the bottom edge using a pencil or marker.
2. Spot the mixture of inks at equidistant points along the baseline using a capillary tube or toothpick.
3. Pour the solvent (mobile phase) into a beaker or glass jar, ensuring that the level of the solvent is below the baseline on the paper strip.
4. Place the paper strip vertically into the solvent, making sure that the spots are above the solvent level.
5. Allow the solvent to ascend the paper by capillary action until it reaches near the top edge. Remove the strip from the solvent and mark the solvent front.
6. Allow the paper to air dry, and then visualize the separated components.
7. Measure the distance traveled by each component from the baseline and the solvent front.

Observations and Calculations:

Based on the observed distances traveled by the components, calculate the Rf (retention factor) values using the formula:

\[ Rf = \frac{{\text{{Distance traveled by the component}}}}{{\text{{Distance traveled by the solvent front}}}} \]

Conclusion

The experiment successfully demonstrated the separation of a given mixture of inks using paper chromatography. By analyzing the migration distances and calculating the Rf values, the individual components of the ink mixture were identified. Paper chromatography is an effective technique for qualitative analysis of mixtures and is widely used in various fields such as forensics, chemistry, and biology.

Precautions

• Handle the chromatography paper with care to avoid tearing or wrinkling.
• Avoid touching the spots on the paper to prevent contamination.
• Use a suitable solvent that provides good separation of the components.
• Ensure that the paper strip is placed vertically in the solvent to allow for uniform separation.
• Allow sufficient time for the solvent to ascend the paper and separate the components adequately.

Short Questions

1. What is paper chromatography?
   Paper chromatography is a technique used to separate mixtures into their individual components based on their differential migration rates through a stationary phase.
2. What is the principle behind paper chromatography?
   Paper chromatography relies on the differential affinity of the components for the mobile phase (solvent) and the stationary phase (paper), causing them to migrate at different rates and separate.
3. Why is it important to draw a baseline on the chromatography paper?
   Drawing a baseline on the chromatography paper helps to accurately spot the mixture and provides a reference point for measuring the migration distances of the components.
4. What is the purpose of spotting the mixture of inks along the baseline?
   Spotting the mixture of inks along the baseline allows for the separation of the components as they migrate through the paper strip in response to the solvent.
5. How does capillary action contribute to paper chromatography?
   Capillary action allows the solvent to ascend the paper strip, carrying the components of the mixture along with it, thereby facilitating their separation based on differential migration rates.
6. What is Rf value in paper chromatography?
   Rf value (retention factor) is a measure of the distance traveled by a component relative to the distance traveled by the solvent front. It is used to characterize the relative mobility of components in chromatography.
7. How is the Rf value calculated?
   The Rf value is calculated using the formula: Rf = (Distance traveled by the component) / (Distance traveled by the solvent front).
8. What factors can affect the separation of components in paper chromatography?
   Factors such as choice of solvent, type of paper, temperature, humidity, and concentration of the sample can affect the separation of components in paper chromatography.
9. What is the significance of measuring the distance traveled by each component?
   Measuring the distance traveled by each component allows for the calculation of Rf values, which aids in the identification and characterization of the components in the mixture.
10. Why is it important to ensure that the solvent level is below the baseline?
    Ensuring that the solvent level is below the baseline prevents the dissolution of the mixture spots and allows for proper separation of the components as the solvent ascends through the paper.
11. What precautions should be taken to prevent contamination during paper chromatography?
    Precautions such as avoiding touching the spots on the paper, using clean equipment, and maintaining a sterile environment can help prevent contamination during paper chromatography.
12. How can paper chromatography be applied in real-life scenarios?
    Paper chromatography can be applied in various fields such as forensics (to analyze ink samples), food industry (to detect food dyes), pharmaceuticals (to analyze drug components), and environmental science (to test water quality).
13. What are the advantages of using paper chromatography?
    Advantages of paper chromatography include simplicity, low cost, ease of use, and ability to separate a wide range of compounds with high resolution.
14. What are the limitations of paper chromatography?
    Limitations of paper chromatography include low sensitivity, poor reproducibility, limited resolution, and inability to separate closely related compounds.
15. Can paper chromatography be used for quantitative analysis?
    Yes, paper chromatography can be used for qualitative as well as quantitative analysis by measuring the intensities of separated components or by comparing with known standards.
16. What is the role of the solvent in paper chromatography?
    The solvent serves as the mobile phase in paper chromatography, carrying the sample components along the paper strip and facilitating their separation based on differential migration rates.
17. How can the resolution of separation be improved in paper chromatography?
    The resolution of separation in paper chromatography can be improved by using a narrower paper strip, optimizing the choice of solvent and paper type, and increasing the distance traveled by the solvent.
18. What are the different types of stationary phases used in chromatography?
    Different types of stationary phases used in chromatography include paper, silica gel, alumina, cellulose, and ion-exchange resins.
19. How does the choice of solvent affect the separation in paper chromatography?
    The choice of solvent affects the separation in paper chromatography by influencing the solubility and mobility of the sample components, thereby affecting their migration rates and separation efficiency.

Multiple Choice Questions (MCQs)

1. What is the purpose of drawing a baseline on the chromatography paper?
   1. To mark the origin of separation
   2. To provide support to the paper strip
   3. To facilitate accurate spotting of the sample
   4. To enhance the capillary action
   Answer: c) To facilitate accurate spotting of the sample
2. Which factor does not affect the separation of components in paper chromatography?
   1. Choice of solvent
   2. Type of paper
   3. Temperature of the surroundings
   4. Relative humidity
   Answer: b) Type of paper
3. What is the retention factor (Rf) in paper chromatography?
   1. The rate of migration of the solvent
   2. The ratio of the distance traveled by the component to the distance traveled by the solvent front
   3. The total distance traveled by all components
   4. The volume of the solvent used
   Answer: b) The ratio of the distance traveled by the component to the distance traveled by the solvent front
4. Which precaution is necessary to prevent contamination during paper chromatography?
   1. Avoiding the use of pencils or markers
   2. Avoiding touching the spots on the paper
   3. Using a larger volume of sample
   4. Increasing the temperature of the surroundings
   Answer: b) Avoiding touching the spots on the paper
5. What is the role of the solvent in paper chromatography?
   1. To dissolve the stationary phase
   2. To provide support to the paper strip
   3. To separate the components of the mixture
   4. To increase the temperature of the surroundings
   Answer: c) To separate the components of the mixture