Колоночная хроматография
At the end of this lab, students should know...
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Q1: How do you prepare a green food dye solution in ethanol for column chromatography?
Tare a clean 5-mL volumetric flask and add 2.5 g of green food dye. Pour approximately 1.5 mL of 95% ethanol into the flask, stopper it, and invert several times to mix thoroughly. Then fill to the mark with 95% ethanol, reseal, and invert until the color appears uniform throughout. Label the flask with its name and concentration.
Q2: What safety equipment and waste containers are required before starting a column chromatography lab?
Put on a lab coat, safety glasses, and nitrile gloves before beginning. Ensure the lab has labeled waste containers for organic waste, silica gel, and glass. Fill a plastic wash bottle with acetone and place it near the organic waste container for post-lab column cleaning by students or teaching assistants.
Q3: What materials and equipment should be set up at each student workstation for column chromatography?
Each pair of students needs five 50-mL beakers, one 100-mL beaker, graduated cylinders (one 5- or 10-mL and two 50-mL), two powder funnels, a glass stirring rod, laboratory tape, a marking pen, a ruler, and two pipette bulbs. Additionally, ensure a lab stand or scaffold with an appropriate clamp secures the column at each workspace.
Q4: How should the stopcock on a chromatography column be tested and prepared?
Test each stopcock to ensure it fits securely but still turns easily. After testing, close the stopcocks and distribute the columns to student workspaces. Proper stopcock function prevents solvent leakage during the chromatography procedure and ensures accurate separation results throughout the experiment.
Q5: What materials should be placed in the central lab area for student access?
Place the prepared dye solution, a container of silica gel powder, sand, laboratory wipes, clean spatulas, weighing boats, a bottle of 95% ethanol in a nearby hood, glass or cotton wool, at least one long blunt-ended metal or wooden rod, and a box of Pasteur pipettes in the central area for all students to access.
Q6: Why is a well-ventilated area important when setting up materials for column chromatography?
A well-ventilated area is essential when placing silica gel powder, sand, spatulas, and weighing boats near the balance because these materials can generate dust. Additionally, 95% ethanol must be stored in a nearby hood to minimize vapor exposure and ensure safe handling of volatile organic solvents during lab preparation and execution.
Q7: How much dye solution should be prepared for a typical undergraduate lab with 10 students working in pairs?
Prepare 5 mL of green food dye solution in ethanol for 10 students working in pairs, with some excess. This quantity is sufficient for the standard lab setup. Adjust quantities proportionally if your class size differs or if additional practice runs are needed for student learning outcomes.