Lab Procedure

SAFETY NOTES: The Iodine fumes are caustic and should be kept strictly in the hood. Make sure the fingerprint papers are fully "aired" before removing them from the hood area.

Part 1: Identification of Ink Type Using TLC	Each Bench will work as a forensics team. A sample pack is provided to each bench. Be sure to note the identification codes on all pieces of evidence.
	Every team member should put on gloves before handling any evidence.
	Carefully remove the "threatening note" from its evidence bag. Record your observations about the note in your lab notebook.
	With Scissors, carefully cut two small slivers of the writing on the note. You want to have predominantly ink on these samples. Keep in mind that you will be testing this note for fingerprints as well so conserve the evidence as much as possible.
	On another separate piece of paper make test writings with the pens obtained from the suspects. Cut Slivers of ink from each suspect note as above.
	Place each set of ink sample slivers in a different well in a well plate. Add 1-2 drops of methanol to each well. Use as little methanol as possible to extract the ink so that it is not too dilute. Let the plate sit for 1-2 minutes. Shake gently, if necessary, to remove the ink from the papers.
	Prepare a TLC plate by lightly drawing a straight line with a pencil across each plate 1cm from the bottom.
	Spot the plate using capillary tubes by placing them into the extracted samples and drawing out a small amount of solution. 4 spots total = 3 evidence pens for reference and your unknown ink from the note. Apply a small spot, let dry and repeat until a very small, clearly visible spot appears on the plate. Mark the identity of each spot in pencil at the top of the plates. Be careful to not let the spot become too big or your experiment will be ruined.
	Prepare a TLC tank by adding ~25 mL of chromatography solution to a 400 mL Beaker. Place the TLC plate in the TLC Tank in the hood. Watch the solvent front move slowly up the plates. When the solvent is ~3/4 of the way up the plate, remove it from the tank. Mark the solvent line with a pencil. Place the plates in the hood to dry.
	Take the dry plates out of the hood and examine using both visible and UV light. Calculate Rf value for each band.
Part 2: Developing Fingerprints
	Take the rest of the suspect "threatening note" and place a paper clip with a piece of string attached to it onto the top center of the note.
	Tape the string and note to the inside bottom of a 1 Liter beaker so that when the beaker is turned upsidedown, the note will be suspended in the center.
	Take the beaker and note to the hood. Set the Inverted beaker over a watchglass containing iodine crystals. Allow the fingerprints to develop for approximately 3 to 5 minutes.
	Remove the note from the beaker and wave the note around to "air out" any unfixed iodine fumes.
	Take the note back to your lab bench and using the reference fingerprint cards from the background for comparison, make identification (if possible) of the suspect's identity.
Part 3: Fiber Analysis
	Carefully remove the fiber evidence from the evidence bag. Record Observations.
	Cut a small portion of the fiber from the whole sample.
	Holding the fabric with tweezers, not your fingers, over a watchglass, "burn" the fibers using a bunsen burner. Make and Record your observations. Repeat if necessary to draw a conclusion as to the type of fiber (See Background).