LAB REPORT: DATA ANALYSIS Solvent Distance traveled by the solvent (mm) (Solvent Front) Distance travelled by each food
Posted: Sat Jul 09, 2022 12:31 pm
LAB REPORT: DATA ANALYSIS
Solvent
Distance traveled by the solvent (mm)
(Solvent Front)
Distance travelled by each food dye (mm)
Rf = Distance dye traveled/
distance solventfronttraveled
Distilled water
Green:
Blue:
Red/Brown:
Green:
Blue:
Red/Brown:
0.2 % NaCl solution
Green:
Blue:
Red/Brown:
Green:
Blue:
Red/Brown:
0.5 % NaCl solution
Green:
Blue:
Red/Brown:
Green:
Blue:
Red/Brown:
Isopropyl Alcohol
Green:
Blue:
Red/Brown:
Green:
Blue:
Red/Brown:
Pictures of your chromatography papers. Please indicate the solvent used for each paper:
POST-LAB QUESTIONS
Identify the analyte, eluting solvents (mobile phases), and stationary phase used in this experiment. Which solvent provided the best separation?
Chromatography has many applications. Research one application of chromatography and explain how it is used.
Search on the internet to find out if food dyes have any reported or potential health effects.
Heres all the information you need...
EXPERIMENT 8 CHROMATOGRAPHY OBJECTIVES In this experiment, you will • conduct paper chromatography • observe how solvents separate the food dyes in candies. • Calculate retention factor for food dyes INTRODUCTION Have you ever wondered which chemicals are used to produce various colors in candies and food? Some colors can be obtained using a single food coloring whereas others may use a combination of dyes. The paper chromatography is a separation method in which a cellulose filter paper acts as a stationary phase on which the separation of compounds occurs. The stationary phase is made from a solid substance that remains stationary for the mixture. The mobile phase, which may be a liquid or gas, moves the dissolved mixture components through the stationary phase. In this technique, the analyte (a substance whose chemical constituents are being identified and measured) is contained in a mobile phase, and travels through the stationary phase (chromatography paper). The separation occurs as the mobile phase travels along the paper, carrying along with the components with higher affinity for the solvent than the paper. Some of the components will be left behind due to the higher affinity for the cellulose filter paper. In other words, in paper chromatography different dyes will be separated based on their solubility, or their ability to dissolve in mobile phase. The more soluble a pigment is, the more readily it will dissolve in the mobile phase and the farther it will usually travel. In this lab, you will measure how far the food dyes travel on a paper. In addition, you will be separating a food dye dissolved in alcohol based on their affinity to the mobile phase (water) versus the stationary phase (paper). The main component of paper is cellulose, a polymer of carbohydrate, which is represented by the formula (C6H10O5)n. Like water (H-OH), cellulose has multiple polar -OH regions, which enables the paper to form weak bonds to polar solutes. As the solvent moves through the paper by capillary action, the food dye will be carried along with the solvent at various rates. The distance that the ions travel is dependent upon two opposing forces: (1) attraction of the dye molecules for the solvent molecules, and (2) attraction of the dye molecules for the adsorbing material paper. Note that the cellulose surface is negatively charged, and this property of the paper results in attraction of positive charged ions. In addition to the polarities, solubility of the food dye in each phase plays an important role. The affinity of each substance has for the stationary phase can be quantified. The ratio of the distance the solute travels up the paper, compared to the total distance of the mobile phase (solvent), is called the retention factor (Rf), and can be calculated shown below. Chromatography CHM100 Experiment 8 7.2 𝑹𝒇 = 𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒔𝒐𝒍𝒖𝒕𝒆 𝒕𝒓𝒂𝒗𝒆𝒍𝒆𝒅 𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒔𝒐𝒍𝒗𝒆𝒏𝒕 𝒇𝒓𝒐𝒏𝒕 𝒕𝒓𝒂𝒗𝒆𝒍𝒆𝒅 = 𝒄𝒎 𝒄𝒎 = 𝒖𝒏𝒊𝒕𝒍𝒆𝒔𝒔 Example 1. In this chromatogram, only one spot is developed, and its retention factor is calculated as shown below. The distance the solvent front traveled is measured from the pencil line to the solvent front line. Figure 1. Chromatography paper and how to calculate Rf value. 𝑅𝑓 = 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑠𝑜𝑙𝑢𝑡𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑒𝑑 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑠𝑜𝑙𝑣𝑒𝑛𝑡 𝑓𝑟𝑜𝑛𝑡 𝑡𝑟𝑎𝑣𝑒𝑙𝑒𝑑 = 6 𝑐𝑚 12 𝑐𝑚 = 0.5 Review: How to prepare salt solutions Example: Prepare 50 mL of 5.0 wt.% NaCl solution using distilled water. First, we calculate how many grams of NaCl (table salt) you need to dissolve in water. 5.0 wt.% NaCl solution means 5.0 g NaCl in 100 g solution or 100 mL solution. Let’s assume the density of the salt solution is about 1.00 g/mL, same as water. 50 𝑚𝐿 𝑁𝑎𝐶𝑙 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑥 1 𝑔 1 𝑚𝐿 = 50 𝑔 𝑁𝑎𝐶𝑙 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 50 𝑔 𝑁𝑎𝐶𝑙 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑥 5.0 𝑔 𝑁𝑎𝐶𝑙 100 𝑔 𝑁𝑎𝐶𝑙 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 2.5 𝑔 𝑁𝑎𝐶𝑙 (𝑡𝑎𝑏𝑙𝑒 𝑠𝑎𝑙𝑡) 𝑛𝑒𝑒𝑑𝑒𝑑. Solution = solute (NaCl) + solvent (water) 50 g NaCl solution = 2. 5 g NaCl + 47.5 g water In a beaker or a plastic cup, measure 2.5 g of NaCl, and then add water until the total weight (NaCl + water) is 50 g. Make sure to stir the solution so that most of the solid is dissolved in water. Practice: In your experiment, you will need 0.2 % and 0.5 % salt solutions. Show your calculations below: Chromatography CHM100 Experiment 8 7.3 EXPERIMENTAL Equipment Materials clear cups, beaker, graduated cylinder, 11 x 11 cm chromatography papers, plastic spoons, 3 capillary tubes (one for each color) Plastic pipettes scissors to cut paper* Distilled Water* 30 mL Isopropyl alcohol* M&Ms® (blue, green, red or brown)* Table salt (NaCl)* *You need to provide item in red. PROCEDURE Step 1. Put on your safety goggles and gloves. Step 2. Prepare 50 mL 0.2% Sodium Chloride, NaCI solution and 50 mL 0.5% Sodium Chloride, NaCI solution. See example at page 2. Step 3. Obtain three clear cups and label each cup with the color you will be extracting. You will need to place 2-4 M&Ms® into each cup. Do not mix the colors. In the next step, you will dissolve the color coating of the candies by adding a solvent. The food dye is the analyte (a substance whose chemical constituents are being identified and measured). Watch the video posted on blackboard if you wish to see the technique. Step 4. Use a pipette to add 1 mL of isopropyl alcohol to each cup. Then, stir with a plastic spoon until you see the colors of the candies dissolved in the alcohol. To avoid contamination, make sure to use a clean spoon each time you change cups. Keep the candies in the cups until you prepare the stationary phase (chromatography paper). Remove the candies after preparing the chromatography paper and before dipping the capillary tube. Step 5. Cut each piece of chromatography paper in half. You should have total 4 paper now. Using a pencil, draw a pencil line about 1-1.5 cm from the bottom end of each paper as shown in Figure 1. On this line, mark three small dots using a pencil for each color (see Figure 2). Make sure to keep the spots at equal distance. You could label each spot. Figure 2. Preparing chromatography paper. Chromatography CHM100 Experiment 8 7.4 Step 6. Using a capillary tube, place small spots of the analyte (candy solution in the cups) on the marked spot. Since there are three colors to be tested, there will be three spots on the line (use one capillary tube per color; save the tubes for the additional trials). To use the capillary tube, simply place the open end of the tube in the cups. The liquid will be drawn into the tube and will be dispensed onto the marked spot on your paper. Step 7. Allow the spot to dry, and re-spot the analyte in the exact same area as done in Step 6. Repeat this process until the colored dots appear on the paper. You may need to apply 3-4 times. Step 8. Use a graduated cylinder to pour 20 mL distilled water (your eluting solvent) into the beaker. Place the paper vertically with the line-side down in the beaker with the eluting solvent as shown below. Let the water rise up the paper until it is about an inch or two from the top. Remove the paper at this point. (This may take around 5-10 minutes.) This is called solvent front. Keep a close eye on the solvent front and do not let solvent front reach the top of the paper. Figure 3. Chromatography paper in a beaker. You do not need to cover the top. Step 9. Take out the paper and use a pencil to mark the edge of the solvent front (the edge of the mobile phase) and the location of the analytes with a pencil (see Figure 1 for reference). Measure the solvent and dye fronts based on farthest location from origin line. Record your data and any additional observations in data tables. How many dye components does each M&M color have? Step 10. Use tap water to rinse the beaker and then repeat steps 6-9 for the other eluting solvents (0.5% NaCl, 0.2% NaCl, and isopropyl alcohol). Step 11. Label the results of all your chromatography experiments and take a picture of the results. Include this picture in your lab report. Make sure to indicate which the eluting solvent is used in your results.
Solvent
Distance traveled by the solvent (mm)
(Solvent Front)
Distance travelled by each food dye (mm)
Rf = Distance dye traveled/
distance solventfronttraveled
Distilled water
Green:
Blue:
Red/Brown:
Green:
Blue:
Red/Brown:
0.2 % NaCl solution
Green:
Blue:
Red/Brown:
Green:
Blue:
Red/Brown:
0.5 % NaCl solution
Green:
Blue:
Red/Brown:
Green:
Blue:
Red/Brown:
Isopropyl Alcohol
Green:
Blue:
Red/Brown:
Green:
Blue:
Red/Brown:
Pictures of your chromatography papers. Please indicate the solvent used for each paper:
POST-LAB QUESTIONS
Identify the analyte, eluting solvents (mobile phases), and stationary phase used in this experiment. Which solvent provided the best separation?
Chromatography has many applications. Research one application of chromatography and explain how it is used.
Search on the internet to find out if food dyes have any reported or potential health effects.
Heres all the information you need...
EXPERIMENT 8 CHROMATOGRAPHY OBJECTIVES In this experiment, you will • conduct paper chromatography • observe how solvents separate the food dyes in candies. • Calculate retention factor for food dyes INTRODUCTION Have you ever wondered which chemicals are used to produce various colors in candies and food? Some colors can be obtained using a single food coloring whereas others may use a combination of dyes. The paper chromatography is a separation method in which a cellulose filter paper acts as a stationary phase on which the separation of compounds occurs. The stationary phase is made from a solid substance that remains stationary for the mixture. The mobile phase, which may be a liquid or gas, moves the dissolved mixture components through the stationary phase. In this technique, the analyte (a substance whose chemical constituents are being identified and measured) is contained in a mobile phase, and travels through the stationary phase (chromatography paper). The separation occurs as the mobile phase travels along the paper, carrying along with the components with higher affinity for the solvent than the paper. Some of the components will be left behind due to the higher affinity for the cellulose filter paper. In other words, in paper chromatography different dyes will be separated based on their solubility, or their ability to dissolve in mobile phase. The more soluble a pigment is, the more readily it will dissolve in the mobile phase and the farther it will usually travel. In this lab, you will measure how far the food dyes travel on a paper. In addition, you will be separating a food dye dissolved in alcohol based on their affinity to the mobile phase (water) versus the stationary phase (paper). The main component of paper is cellulose, a polymer of carbohydrate, which is represented by the formula (C6H10O5)n. Like water (H-OH), cellulose has multiple polar -OH regions, which enables the paper to form weak bonds to polar solutes. As the solvent moves through the paper by capillary action, the food dye will be carried along with the solvent at various rates. The distance that the ions travel is dependent upon two opposing forces: (1) attraction of the dye molecules for the solvent molecules, and (2) attraction of the dye molecules for the adsorbing material paper. Note that the cellulose surface is negatively charged, and this property of the paper results in attraction of positive charged ions. In addition to the polarities, solubility of the food dye in each phase plays an important role. The affinity of each substance has for the stationary phase can be quantified. The ratio of the distance the solute travels up the paper, compared to the total distance of the mobile phase (solvent), is called the retention factor (Rf), and can be calculated shown below. Chromatography CHM100 Experiment 8 7.2 𝑹𝒇 = 𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒔𝒐𝒍𝒖𝒕𝒆 𝒕𝒓𝒂𝒗𝒆𝒍𝒆𝒅 𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒔𝒐𝒍𝒗𝒆𝒏𝒕 𝒇𝒓𝒐𝒏𝒕 𝒕𝒓𝒂𝒗𝒆𝒍𝒆𝒅 = 𝒄𝒎 𝒄𝒎 = 𝒖𝒏𝒊𝒕𝒍𝒆𝒔𝒔 Example 1. In this chromatogram, only one spot is developed, and its retention factor is calculated as shown below. The distance the solvent front traveled is measured from the pencil line to the solvent front line. Figure 1. Chromatography paper and how to calculate Rf value. 𝑅𝑓 = 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑠𝑜𝑙𝑢𝑡𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑒𝑑 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑠𝑜𝑙𝑣𝑒𝑛𝑡 𝑓𝑟𝑜𝑛𝑡 𝑡𝑟𝑎𝑣𝑒𝑙𝑒𝑑 = 6 𝑐𝑚 12 𝑐𝑚 = 0.5 Review: How to prepare salt solutions Example: Prepare 50 mL of 5.0 wt.% NaCl solution using distilled water. First, we calculate how many grams of NaCl (table salt) you need to dissolve in water. 5.0 wt.% NaCl solution means 5.0 g NaCl in 100 g solution or 100 mL solution. Let’s assume the density of the salt solution is about 1.00 g/mL, same as water. 50 𝑚𝐿 𝑁𝑎𝐶𝑙 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑥 1 𝑔 1 𝑚𝐿 = 50 𝑔 𝑁𝑎𝐶𝑙 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 50 𝑔 𝑁𝑎𝐶𝑙 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑥 5.0 𝑔 𝑁𝑎𝐶𝑙 100 𝑔 𝑁𝑎𝐶𝑙 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 2.5 𝑔 𝑁𝑎𝐶𝑙 (𝑡𝑎𝑏𝑙𝑒 𝑠𝑎𝑙𝑡) 𝑛𝑒𝑒𝑑𝑒𝑑. Solution = solute (NaCl) + solvent (water) 50 g NaCl solution = 2. 5 g NaCl + 47.5 g water In a beaker or a plastic cup, measure 2.5 g of NaCl, and then add water until the total weight (NaCl + water) is 50 g. Make sure to stir the solution so that most of the solid is dissolved in water. Practice: In your experiment, you will need 0.2 % and 0.5 % salt solutions. Show your calculations below: Chromatography CHM100 Experiment 8 7.3 EXPERIMENTAL Equipment Materials clear cups, beaker, graduated cylinder, 11 x 11 cm chromatography papers, plastic spoons, 3 capillary tubes (one for each color) Plastic pipettes scissors to cut paper* Distilled Water* 30 mL Isopropyl alcohol* M&Ms® (blue, green, red or brown)* Table salt (NaCl)* *You need to provide item in red. PROCEDURE Step 1. Put on your safety goggles and gloves. Step 2. Prepare 50 mL 0.2% Sodium Chloride, NaCI solution and 50 mL 0.5% Sodium Chloride, NaCI solution. See example at page 2. Step 3. Obtain three clear cups and label each cup with the color you will be extracting. You will need to place 2-4 M&Ms® into each cup. Do not mix the colors. In the next step, you will dissolve the color coating of the candies by adding a solvent. The food dye is the analyte (a substance whose chemical constituents are being identified and measured). Watch the video posted on blackboard if you wish to see the technique. Step 4. Use a pipette to add 1 mL of isopropyl alcohol to each cup. Then, stir with a plastic spoon until you see the colors of the candies dissolved in the alcohol. To avoid contamination, make sure to use a clean spoon each time you change cups. Keep the candies in the cups until you prepare the stationary phase (chromatography paper). Remove the candies after preparing the chromatography paper and before dipping the capillary tube. Step 5. Cut each piece of chromatography paper in half. You should have total 4 paper now. Using a pencil, draw a pencil line about 1-1.5 cm from the bottom end of each paper as shown in Figure 1. On this line, mark three small dots using a pencil for each color (see Figure 2). Make sure to keep the spots at equal distance. You could label each spot. Figure 2. Preparing chromatography paper. Chromatography CHM100 Experiment 8 7.4 Step 6. Using a capillary tube, place small spots of the analyte (candy solution in the cups) on the marked spot. Since there are three colors to be tested, there will be three spots on the line (use one capillary tube per color; save the tubes for the additional trials). To use the capillary tube, simply place the open end of the tube in the cups. The liquid will be drawn into the tube and will be dispensed onto the marked spot on your paper. Step 7. Allow the spot to dry, and re-spot the analyte in the exact same area as done in Step 6. Repeat this process until the colored dots appear on the paper. You may need to apply 3-4 times. Step 8. Use a graduated cylinder to pour 20 mL distilled water (your eluting solvent) into the beaker. Place the paper vertically with the line-side down in the beaker with the eluting solvent as shown below. Let the water rise up the paper until it is about an inch or two from the top. Remove the paper at this point. (This may take around 5-10 minutes.) This is called solvent front. Keep a close eye on the solvent front and do not let solvent front reach the top of the paper. Figure 3. Chromatography paper in a beaker. You do not need to cover the top. Step 9. Take out the paper and use a pencil to mark the edge of the solvent front (the edge of the mobile phase) and the location of the analytes with a pencil (see Figure 1 for reference). Measure the solvent and dye fronts based on farthest location from origin line. Record your data and any additional observations in data tables. How many dye components does each M&M color have? Step 10. Use tap water to rinse the beaker and then repeat steps 6-9 for the other eluting solvents (0.5% NaCl, 0.2% NaCl, and isopropyl alcohol). Step 11. Label the results of all your chromatography experiments and take a picture of the results. Include this picture in your lab report. Make sure to indicate which the eluting solvent is used in your results.