Ink Analysis and Thin Layer Chromatography TLC

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Ink Analysis and Thin Layer Chromatography (TLC)
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Ink Analysis

• Objectives
• Explain the process of thin layer chromatography
• Know the components of ink

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What is Ink?

• Several organic dyes- blue, red, black (form an
  ink fingerprint)
• Tags that signify the manufacturing year-
  isotopes

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Why is Ink important Forensically?

• Fraud Cases
• Embezzlement
• Theft
• Kidnapping and Ransom
• Threats
• Documentation

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How is Ink used as a forensic tool ?

• Small sample is dissolved
• Unknown sample compared to known sample
• Each pen manufacturer has its own recipe for ink
• Tags in ink can determine the year the pen was
  manufactured

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What is Thin Layer Chromatography (TLC) ?

• Qualitative analysis
• Separates mixtures into individual parts
• like dissolves like - polar (opposite) vs.
  non-polar (alike)
• Mobile phase (solvent) vs. stationary stage
  (paper)

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TLC PAPER SET-UP

• P S1 S2 K1 K2 K3 CS

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Ink Lab- compare three known pens and compare to
the unknowns.

• Measure 0.5 cm from the top and bottom of the
  chromatography paper
• Lightly draw a line across the paper at these
  points IN PENCIL
• Determine where you will place your seven samples
  by marking, under your pencil line, where the ink
  samples will go
• For the three known samples, the principals pen
  and the two suspect pens, place a small amount of
  ink above your labeled paper. Firmly press down
  on the paper with the pen. You want to make a
  small dot.

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Ink Lab- compare three known pens and compare to
the unknowns.

• For the crime scene sample, see the teacher once
  youve set up your paper with pencil marks
• Staple the ends of the chromatography paper
  together with the ink marks on the outside. DO
  NOT overlap the paper.
• Add about 5 mL of a alcohol/water solution
  (premixed 21 by the teacher) to a petri dish
• Place the paper inside the petri dish. DO NOT
  let the chromatography paper touch the side of
  the dish.
• Place the chromatography paper in the solution

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Ink Lab- compare three known pens and compare to
the unknowns.

• After 20-25 minutes, the mobile phase will end.
• Remove your chromatography paper from the petri
  dish when the liquid is at the pencil line.
• Using a pencil, circle the points where the ink
  has traveled and separated.
• Dispose of the solution by running water and
  pouring it slowly down the sink.
• Hang your chromatography paper up to dry.