Paper Chromatography Lab

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Goodwin College *

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101

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Chemistry

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Apr 3, 2024

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docx

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Uploaded by JusticePartridge3570

©2018, eScience Labs Pre-Lab Questions 1. Rank the following solutions from least polar to most polar. Rank on a scale of 1-4: 1 being the least polar and 4 being the most polar. _______ 50% ISOPROPANOL / H 2 O _______ 25% ISOPROPANOL / H 2 O _______ PURE WATER _______ 75% ISOPROPANOL / H 2 O 2. Identify the analyte, eluting solvents (mobile phases), and stationary phase used in Experiment 1. 3. Why would it be important to know which food dyes are in food?

Experiment Inventory Materials Eluting Solvents Labware (3) 50 mL Beakers • 30 mL 0.5% Sodium Chloride, NaCI solution100 mL Graduated Cylinder • 30 mL 0.2% Sodium Chloride, NaCI solution500 mL Beaker • *30 mL Distilled Water 3 Popsicle Sticks • *30 mL Isopropyl Alcohol, C 3 H 8 O 3 Capillary Tubes (packaged inside a test tube) (2) 11 x 11 cm Pieces of Chromatography Paper Ruler *6 M&Ms® (2 blue, 2 green, 2 red) *Scissors *Pencil *Computer with Internet Access *Camera / Smart Phone *Tap Water Note: You must provide the materials listed in *red. ©2018, eScience Labs Experiment Pa 1 per Chromatography EXPERIMENT 1: PAPER CHROMATOGRAPHY In this experiment, you will use paper chromatography to determine the R f value for the dyes found in candy-coated chocolate pieces. The chromatography paper acts as the stationary phase for the procedure, and a variety of mobile phases will be tested. Multiple tests with different eluting solvents must be run to determine the best eluting solvent to separate the food dyes. PROCEDURE 1. Put on your safety glasses and gloves (provided in your safety box). 2. Gather three 50 mL beakers, one for each color candy you will test. 3. Place 2 M&Ms® candies of one color into a 50 mL beaker. 4. Repeat for each color of the candy you will test. You should have two green candies in one beaker, two red candies in a second beaker, and two blue candies in the third beaker. Part 1: Preparation of the Analyte 1. Use a pipette to add 1 mL of isopropyl alcohol to each 50 mL beaker. 2. Stir with a popsicle stick for one minute (the colors may not appear to be very dark). Remove the candies. Be sure to use a clean popsicle stick each time you change beakers.

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©2018, eScience Labs Part 2: Preparation of Stationary Phase 1. Cut each piece of chromatography paper in half. Direction doesn’t matter, but keep it consistent for all papers. 2. Set up the chromatography paper according to Figure 10. 3. Using a pencil, mark the paper 1 cm from the bottom edge. Refer to Figure 10. 4. Using a capillary tube, place small spots of the analyte equal distance apart on the marked line. 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). Note : Capillary tubes are extremely thin tubes. They are useful when working with very small amounts of a sample, and collect liquid samples through capillary action. To use the capillary tube, simply place the open end of the tube in the sample. The liquid molecules will be drawn into the tube and stick to the inner walls. Figure 11 provides a references for this process. 5. Allow the spot to dry, and re-spot the analyte in the exact same area as done in Step 4. Repeat this process at least five times, or until the colored dots appear on the paper. 6. Use a 100 mL graduated cylinder to pour 20 mL distilled water (your eluting solvent) into the 500 mL beaker. 7. Place the paper vertically with the line-side down in the 500 mL beaker with the eluting solvent. Let it stand for 3–5 minutes (Figure 12). 8. 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 10 for reference). Measure the solvent and dye fronts based on farthest location from origin line. Record your data and any additional observations in Table 2. 9. Use tap water to rinse the 500 mL beaker and then repeat steps 4-8 for the remaining eluting solvents (0.5% NaCl, 0.2% NaCl, and isopropyl alcohol), record your data in Table 2. 10.Line up the results of all your chromatography experiments and use your camera (or smart phone) to take a picture of the results. Be sure to correctly label the picture and send it to your instructor along with the answers to the lab questions. Figure 10. Chromatography set up. Figure 11 . Capillary tubes use capillary action to pull up liquid. Figure 12. Eluting solvent set up.

©2018, eScience Labs Data Sheet Experiment 1 Data Sheet Table 2: Paper Chromatography Data and Observations Solvent Distance Traveled by Mobile Phase (mm) Distance Traveled by Each Analyte (mm) R f Value Additional Observations 1: Distilled Water Green: Blue: Red: Green: Blue: Red: 2: 0.5% NaCl Solution Green: Blue: Red: Green: Blue: Red: 3: 0.2% NaCl Solution Green: Blue: Red: Green: Blue: Red: 4: 70% Isopropyl Alcohol Green: Blue: Red: Green: Blue: Red: POST-LAB QUESTIONS 1. Which solvent provided the best separation? 2. Explain which characteristics of the solvent were used to effectively separate the analytes. 3. Some children have reactions to Yellow 5 or Yellow 6 dye. Yellow 5 is a pale yellow color and Yellow 6 is more orange. Use the colors seen on the chromatograms to determine which M&Ms® candies you tested contain Yellow 5. 4. Chromatography has many applications. Research one application of chromatography and explain how it is used and what characteristic is utilized for the separation of the analyte(s).