Safranin O (also known as Basic Red 2) is a fluorescent dye stain primarily used to enhance cyanoacrylate-developed latent fingerprints. This means it's often applied in a sequence after cyanoacrylate fuming has already occurred.
- Fluorescence: Safranin O absorbs light in the green range (around 500 nm) and emits fluorescence in the orange-red range. This makes it ideal for use with a forensic light source in the green spectrum and orange/red filters for viewing and photography.
- Enhancement: It can significantly improve the visibility and contrast of cyanoacrylate-developed prints, particularly on textured or multicolored backgrounds.
Equipment
- Fume hood or well-ventilated area: Working with the chemicals involved requires proper ventilation.
- Glass beakers or containers: For mixing the solution.
- Spray bottle, dip tank, or squirt bottle: For applying the Safranin O solution to the evidence.
- Forensic light source: A light source capable of emitting around the 500 nm wavelength (green).
- Orange or red filters: For viewing and photographing the fluorescence.
- Protective gloves and lab coat: To avoid skin contact with the chemicals.
- Safety goggles: For eye protection.
Ingredients and Quantities for a 1-Liter Solution of Safranin O
- Safranin O Powder: 1 gram
- Ethanol (or Methanol): 1000 ml (1 liter)
Mixing Procedure for Safranin O
- Safety: Put on protective gloves, goggles, and a lab coat. Work in a fume hood or well-ventilated area.
- Weighing: Measure out 1 gram of Safranin O powder.
- Dissolving: Add the Safranin O powder to the 1000 ml ethanol (or methanol) in a glass beaker.
- Stirring: Use a stirring rod or magnetic stirrer to dissolve the powder completely.
- Storage: Transfer the solution to a clean, labeled bottle. A dark glass bottle is ideal.
Latent Print Processing Using Safranin O
- Cyanoacrylate Development: Ensure the latent prints have been thoroughly developed with cyanoacrylate fuming before applying Safranin O.
- Application:
- Spraying: Fine mist application with a spray bottle provides good control.
- Dipping: For smaller items, a dip tank may be used.
- Squirt Bottle: A less precise, but convenient method for targeted application.
- Rinse: Gently rinse excess Safranin O with distilled water. Do not over-rinse, as some staining is needed for fluorescence.
- Air Dry: Allow the item to air dry completely in a dark environment.
- Examination: Examine the treated item under a forensic light source with appropriate filters. Document any fluorescent fingerprints photographically.
Storage and Shelf Life
- Storage: The Safranin O solution is sensitive to light. Store it in a dark glass bottle, ideally in a cool place.
- Shelf Life: A properly stored Safranin O solution should have a shelf life of approximately six months to a year. Monitor it for any signs of precipitation or degradation.