Synthesis of Luminol

Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA

1. Preparation of SolutionsExpand

   Here, we show the laboratory preparation for 10 students working in pairs, with some excess. Please adjust quantities as needed.

   • Before you get started, put on a lab coat, splash-proof safety glasses, and nitrile gloves. The chemicals that you will use are hazardous, so both solutions must be prepared and handled in a fume hood.
   • Prepare 10 mL of a 10% by volume solution of hydrazine in water. Measure 8.4 mL of deionized water and add it to a 30-mL beaker.
   • Measure 1.6 mL of hydrazine hydrate and pour it into the beaker for a total volume of 10 mL. Stir the hydrazine solution with a glass rod until it is well mixed. Note: Hydrazine is flammable, toxic, and explosive.
   • Pour the solution into a 20-mL glass bottle. Cap it and label it with the solution's name and concentration. Store the hydrazine hydrate and the hydrazine solution in a cabinet for flammables.
   • Prepare 20 mL of 2.8 to 3 M aqueous NaOH. Note: NaOH is highly corrosive. Avoid skin contact.
   • Measure 2.2 to 2.4 g of solid NaOH and add it to a 50-mL beaker. Add 20 mL of deionized water and stir the mixture on a stir plate until the NaOH has completely dissolved.
   • Pour the solution into a 20-mL glass bottle and close it with a lid. Label the bottle with the solution's name and approximate concentration. Store the NaOH pellets and solution in the appropriate cabinets.
   • Lastly, clean your glassware following your usual procedures.
2. Preparation of the LaboratoryExpand
   • Before you set up the main lab, reserve a separate room that you can make as dark as possible.
   • Prepare a container for fluorescein waste and ensure that a glass waste container is available.
   • Set out a 10% sodium hypochlorite (bleach) solution and a 1 M sodium carbonate solution in the waste hood.
   • Fill a wash bottle with deionized water and place it in the same hood. Confirm that there are paper towels and a test tube brush by each sink in the main lab.
   • Bring containers of 3-nitrophthalic acid, anhydrous sodium dithionite, solid potassium hydroxide, and fluorescein to the balance area.
   • Confirm that there are enough laboratory wipes, spatulas, and weighing boats for the class.
   • Set triethylene glycol, the hydrazine solution, the NaOH solution, glacial acetic acid, and dimethyl sulfoxide in a central hood. Place a 1-mL graduated pipette and a pipette controller designated for hydrazine in the same hood.
   • Put Pasteur pipettes, filter papers, scissors, and plastic paraffin film in a central area.
   • Set out the following glassware and equipment at each student lab station (we suggest that students work in pairs):

     1    Stirring hotplate

     1    Bunsen burner with tubing

     2    Lab stands

     3    Clamps

     1    Pair of flask tongs

     4    10-mL graduated cylinders

     1    50-mL graduated cylinder

     3    25-mL Erlenmeyer flasks

     1    250-mL filter flask

     1    50-mL beaker

     2    250-mL beakers

     1    400-mL beaker

     1    600-mL beaker

     2    25-mL test tubes

     2    Büchner funnels

     1    Long glass stirring rod

     1    Medium stir bar

     2    Thermometers

     2    Spatulas

     6    Boiling chips

     1    Medium filter adapter

     1    Test tube stopper

     1    Small flask stopper

     1    Pair of tweezers

     1    Fire striker or lighter

     1    Roll of laboratory tape or labels

     2    Pipette bulbs

     1    Pen