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Ink Analysis

Ink Analysis. Introduction to Ink Analysis. Although all blue or black inks may look the same, there can be some important differences in their chemical composition. Analysis of documents under a microscope can be informative as a first step.

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Ink Analysis

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  1. Ink Analysis

  2. Introduction to Ink Analysis • Although all blue or black inks may look the same, there can be some important differences in their chemical composition. • Analysis of documents under a microscope can be informative as a first step. • Thin layer chromatography (TLC) may be necessary to identify the chemical composition.

  3. What is Ink? • Several organic dyes - blue, red, black, etc. (This can form an ink "fingerprint.") • Tags that signify the manufacturing year - isotopes.

  4. Why is Ink Important in Forensics? · Fraud cases
· Embezzlement
· Theft
· Kidnapping and Ransom
· Threats
· Documentation

  5. How is Ink Used as a Forensics Tool? · A small sample is dissolved. 
· This sample is compared to a known sample. 
· Each pen manufacturer has its own "recipe" for ink, so a sample from a document can lead to the discovery of the type of pen used. 
· The tags in ink can determine the year the pen was manufactured.

  6. What is thin layer chromatography (TLC)? • Qualitative analysis. - Using mostly our vision and some measurements of distance on the stationary phase.

  7. What is thin layer chromatography (TLC)? • Separates mixtures into individual parts. • Samples are placed on material that carries the various components in the ink different distances based on their different polarities.

  8. What is thin layer chromatography (TLC)? • Mobile phase vs. stationary phase. • Mobile phase= The liquid or gas that moves up the stationary phase and dissolves the sample. • Solvents can vary and are chosen based on sample type. • Stationary Phase: The solid that the sample is placed on. Silica gel is often used.

  9. Stationary Phase

  10. What separates the compounds as a chromatogram develops? • As the solvent begins to soak up the plate, it first dissolves the compounds in the spot that you have put on the base line. • The compounds present will then tend to get carried up the chromatography plate as the solvent continues to move upwards.

  11. What is thin layer chromatography (TLC)? • "Like dissolves like" - polar vs. non-polar. • The OH groups on the silica gel are very polar and can hydrogen bond. • The sample will also dissolve in the solvent (mobile phase) and move up the plate. • The more able to form H-bond, the more likely the sample will move slower and not as far up. The greater the solubility in the solvent, the faster it will move up the plate.

  12. How fast the compounds get carried up the plate depends on two things: • How soluble the compound is in the solvent. This will depend on how much attraction there is between the molecules of the compound and those of the solvent. • How much the compound sticks to the stationary phase - the silica get, for example. This will depend on how much attraction there is between the molecules of the compound and the silica gel.

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