FORENSICS LAB ONE Ink Chromatography Classified and privileged

FORENSICS LAB № ONE Ink Chromatography Classified and privileged material. Requires security clearance GCS 900.

Name _____________________ Date _________ Period ______ Background Information The word chromatography comes from the Greek “chromos” meaning colour, and “graphy” meaning writing or picture. As such, what we are going to do today is make a colourful picture, using simple inks and solvents. The basic concept of chromatography is really quite simple. The ink in pens is usually one colour, but it is made out of many different compounds, each a different colour. When all the compounds are added together, the desired ink colour – be it black, blue, or any other – is achieved. We can separate the various compounds in ink by using a solvent. A solvent is usually very volatile, meaning that it becomes a vapour very easily, and can be either polar or non-polar. The two solvents that are most commonly used in ink chromatography are water and either ethyl or isopropyl alcohol. This technique can be used in forensics to analyze the ink from notes or letters found at the crime scene. A small sample is taken, and the paper is dipped in the solvent. The solvent travels up the paper, carrying each compound a different distance, depending on how much the solvent is attracted to the compound. The result is a chromatogram, and can be compared to other chromatograms to be admitted as evidence. Safety Precautions Safety is, of course, our paramount concern. You must also have respect for the crime scene. The chemicals we are working with are not particularly dangerous. Observe the following precautions, however: • Never mix chemicals unless instructed to do so by your teacher. • Do not inhale the vapours from any chemicals in this lab. • Treat glassware with care Procedure 1. Observe the note that has been found at the crime scene. Make any preliminary observations in table 1. 2. Pick a pen that you think may have written the note. 3. Cut a strip of filter paper that is about 3 cm. wide, and at least 10 cm long. 4. Using then pen that you have chosen record its number in table 1, make a dark line about 3 cm above the bottom of the strip. Make sure that you transfer a goodish amount of ink to the paper. 5. Tape the paper to a glass rod, so that the bottom tip of the paper just touches the bottom of a large beaker. 6. Fill the beaker with about 2 cm of the solvent. You may choose either water, alcohol, or both. If you choose to do both, you must use TWO SEPARATE BEAKERS and TWO SEPARATE INK SAMPLES. 7. Complete your set up as demonstrated in figure 1. 8. Wait about 20 minutes, or until the solvent is about half way up the slice of paper. 9. Remove your slice of paper from the solvent, and dispose of the solvent in the sink. 10. Compare your chromatogram with the chromatogram that your teacher has prepared from the note that was collected at the scene. Was yours the pen responsible? Record your observations in table 2.

Glass rod Filter paper Ink to be tested Solvent Figure 1. Set up for ink chromatography Pen No. ____ Table 1. Observations of note found at crime scene Affix your chromatogram here Table 2. . Comparison of your chromatogram to the suspect chromatogram

Analysis 1. What techniques did we use today that would be considered good forensic science? 2. What techniques did we use today that might have made our evidence inadmissible in court? 3. This technique is commonly used in forensic labs to analyze notes found at crime scenes. What other applications might it have in the field of forensics? 4. We often use chromatography in the bio lab to separate pigments from plant leaves or to determine the structure of other compounds, such as anthocyanins. How might this type of chromatography be helpful in a criminal investigation? 5. This process requires that the original note (a slice of evidence) be destroyed so that the test can be conducted. What should be done BEFORE ink chromatography to make sure that as much evidence as possible is preserved?