Rhodamine 6G (R6G) is a powerful xanthene dye renowned for its fluorescent properties and commonly used in forensic laboratories after cyanoacrylate ester (superglue) fuming. When applied to cyanoacrylate residues, it excites under specific wavelengths of light (primarily green), making previously invisible or weakly developed latent prints fluoresce a vibrant yellow-orange.
Equipment
- Gloves: Nitrile or latex gloves to protect your hands.
- Safety Glasses: Eye protection is crucial, particularly when working with lasers or alternate light sources.
- Dark Container: To store the R6G solution.
- Spray Bottle, Beaker, or Tray: For application via spraying, dipping, or swabbing.
- Laser or Powerful Alternate Light Source (ALS): R6G works best with lasers in the green spectrum (around 532nm) or an ALS with similar specifications.
- Orange or Yellow Filter Goggles: These goggles filter out background light and significantly enhance the visibility of the fluorescing latent print.
Making a Rhodamine 6G Solution
Here's a standard recipe and guidelines for making a 1-liter working solution of Rhodamine 6G. You have some flexibility as solutions can be made using water or an alcohol solvent, each with its advantages.
Ingredients:
- Rhodamine 6G Powder: 1 gram
- Methanol or Distilled Water: 1 liter
Solvent Considerations:
- Methanol: Works well with most surfaces. Ensure adequate ventilation during use.
- Distilled water: Recommended for porous or varnished surfaces to avoid damage.
Mixing Procedure
- Cleanliness is Key: Ensure all equipment used for mixing is thoroughly cleaned and dried.
- Solvent: Select methanol or water based on the surfaces you will treat.
- Measure: Accurately measure out 1 liter of methanol or distilled water and pour it into a suitable container.
- Rhodamine 6G: Slowly add 1 gram of Rhodamine 6G powder to the solvent.
- Dissolve: Stir the solution gently, preferably with a magnetic stirrer, until the Rhodamine 6G is completely dissolved.
- Label: Properly label the bottle with the reagent name, date of preparation, preparer's initials, and an expiration date (guidance on this below).
Processing Latent Prints with Rhodamine 6G
- Cyanoacrylate Fuming: Process the item first with cyanoacrylate ester (superglue) fuming to develop latent prints.
- Application: Once fuming is complete, carefully apply the Rhodamine 6G via dipping, spraying, or swabbing (if targeting a specific area). Ensure the item is adequately coated.
- Rinsing (Optional): This step depends on the solvent used:
- Methanol: Briefly rinse with methanol to remove excess dye.
- Water: A water rinse may be used or allow to air dry.
- Excitation and Viewing: Examine the item under a laser or ALS using the appropriate filter goggles to visualize any fluorescing latent prints.
Storage and Shelf Life of Rhodamine 6G
- Light Sensitivity: Store R6G in a dark, opaque bottle to protect it from light degradation.
- Temperature: Room temperature storage is generally fine.
- Shelf Life:
- Rhodamine 6G Powder: Has a long shelf life when stored correctly.
- Water-based solutions: These degrade more quickly, prepare smaller batches to ensure use within a reasonable timeframe (weeks to months).
- Methanol-based solutions: Slightly more stable than water-based ones. May last for several months or up to a year if stored properly. Always monitor your solution's quality.
Important Disclaimers
- Always consult your laboratory's specific protocols and safety guidelines.
- Wear appropriate personal protective equipment (PPE).
- Variations in R6G preparation exist – research to find what works best for your lab.