Question 1

What safety equipment is required when preparing dye solutions for UV-Vis spectroscopy?

Accepted Answer

Always wear a lab coat, safety glasses, and nitrile gloves when preparing dye solutions. Since some solutions use hexane or dimethylformamide, prepare those solutions in a fume hood to minimize inhalation exposure. Proper personal protective equipment protects you from chemical contact and vapors during the preparation process.

Question 2

How do you prepare a 1 mM fluorescein stock solution?

Accepted Answer

Measure 0.0166 g of fluorescein and place it in a 50-mL volumetric flask. Add approximately 30 mL of deionized water and swirl until the solid dissolves as much as possible. Fill the flask to the line with deionized water, stopper it, and invert several times while holding the stopper firmly to ensure thorough mixing.

Question 3

Why should dye stock solutions be wrapped in aluminum foil after preparation?

Accepted Answer

Dyes are light-sensitive compounds that degrade when exposed to light. Wrapping stock solutions in aluminum foil protects the dye from light exposure, preserving its concentration and ensuring accurate results during spectroscopic analysis. Label both the flask and the foil exterior for clear identification.

Question 4

What is the correct procedure for diluting a stock solution to create a 3 µM test solution?

Accepted Answer

Use a micropipette to transfer 150 µL of the 1 mM stock solution to a clean 50-mL volumetric flask. Add approximately 30 mL of deionized water and swirl to mix. Fill the flask to the line with deionized water, stopper it, and invert several times until well mixed. This creates a 3 µM test solution from the concentrated stock.

Question 5

How should prepared dye solutions be stored after the lab preparation is complete?

Accepted Answer

Store prepared dye solutions in a refrigerator if one is available to extend shelf life and maintain solution stability. If refrigeration is not available, store solutions at room temperature for up to 24 hours. Proper storage conditions preserve dye concentration and prevent degradation before spectroscopic analysis.

Question 6

What steps should be taken to prepare the spectrometer before students begin the UV-Vis spectroscopy lab?

Accepted Answer

Turn on the UV-Vis spectrometer and instrument computer 10 to 20 minutes before the lab begins. Configure the default scan settings to measure absorbance with a wavelength range of 200–800 nm. Create a dedicated folder for student data and set the default file path to that location so students can save their spectra efficiently.

Question 7

What materials and solvents should be organized in the fume hood during lab preparation?

Accepted Answer

Place organic and aqueous waste containers in the fume hood along with a glass waste container and a 250-mL wash bottle filled with acetone. Add the dye solutions, hexane, and dimethylformamide containers, plus another wash bottle with deionized water. Keep Pasteur pipettes, pipette bulbs, and lab wipes nearby for easy access during the experiment.

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