Question

Laboratory Instructions

Laboratory: Paper Chromatography
Materials
Supplied
• Student Guide
• Laboratory Guidelines
• Paper Chromatography Virtual Lab (online)
Not supplied
• scientific calculator (optional)
Safety
• Review the Laboratory Guidelines before conducting the lab.
Crime Summary
Six-year-old Haley Jones is the daughter of Henry and Sally Jones. Mr. and Mrs. Jones are investment bankers with a local firm, and the family income exceeds $1.2 million. On the way home from school, Haley was abducted. The next morning, a ransom note was submitted to the Jones family. The ransom note included drawings, which looked like Haley’s work.
FBI agents were called in to investigate the case. They took samples of the ink in the ransom note and sent them to a forensic lab for testing. The agents advised Henry Jones to deliver the ransom as directed. Fortunately, the kidnappers released Haley Jones once they received the money.
The FBI agents continued their investigation of the kidnapping by questioning Haley. Her testimony led the agents to an abandoned apartment. They found three marker pens among the evidence inside. Haley said that her captors had given these markers to her when they asked her to draw the pictures on the ransom note.
Can forensic scientists confirm that the three markers found in the abandoned apartment were the ones used in the ransom note? In this lab, you will use paper chromatography to analyze the markers found at the abandoned apartment. You will calculate the retention factors for each substance in the markers. You will then compare these retention factors to those obtained from the ransom note.
Procedure
Use the Image Analyzer (NOTE: The Image Analyzer is in Lesson 2.29) to view the images of black ink paper chromatography results with each of the following solvents:
• alcohol
• vegetable oil
The three markers found at the abandoned apartment are labeled 1-3. The ink from the ransom note is labeled U. The solvent front is labeled at the top of the paper.
Compare Solvents
1. Compare the results using each solvent.
Determine values.
1. Measure the height of the solvent front using the Measuring Tool in the Image Analyzer. Record this value in the table below.
2. Now look at the top pink spot. Measure the height at the center of the spot. Record the value in the table below.
3. Repeat Step 2 for the red spot and the deep red streak on the chromatogram. Take all measurements from the center of the spot or streak.
4. Complete the table by obtaining the measurements for the spot or streaks from the black marker and the green marker.
5. Use the following ratio to calculate the value of each substance.

Paper Chromatography Results
Color Marker 1: Distance (cm) Marker 1:
Marker 2: Distance (cm) Marker 2:
Marker 3: Distance (cm) Marker 3:
Marker U:
Distance (cm) Marker U:

red
yellow
dark blue
light blue
purple
solvent front
Completion of Table = 15 points
Compare values
Compare the results of the markers 1-3 with the marker U. Tip: When you compare these results, you are not looking for exact matches. There will be normal variations based on experimental techniques and measurements.
Analyze the Results
For each question below, support your answer with evidence.
1. Why is it important to use a good solvent for paper chromatography? (5 pts)

Answer here.

2. Which of the markers may have been used in the ransom note? (5 pts)

Answer here.


3. Is the retention value class evidence or individualized evidence? (5 pts)

Answer here.

Answer 1

In paper chromatography, forensic scientists can analyze markers found in the abandoned apartment and compare them to the ink in the ransom note to determine if they match. Using a good solvent is important for effective separation and accurate results. The retention values obtained from the chromatograms are considered class evidence and can help identify which marker may have been used in the ransom note.

Step-by-step explanation:

Paper chromatography is a technique used to separate mixtures, such as inks, by using a porous paper and a solvent. In this lab, the forensic scientists are using paper chromatography to analyze the markers found at the abandoned apartment and compare them to the ink in the ransom note. By measuring the distance each substance travels on the chromatogram, they can calculate the retention factors. These retention factors can help determine if the markers found in the apartment were used in the ransom note.

1. It is important to use a good solvent for paper chromatography because different solvents can dissolve different components of a mixture. If the solvent used is not appropriate, it may not be able to separate the components effectively. For example, if a solvent is too polar, it may cause all the components to travel together, resulting in poor separation.

2. By comparing the results of the markers found in the abandoned apartment with the ink in the ransom note, the forensic scientists can determine which marker was likely used. They can compare the retention factors of each substance in the markers to those obtained from the ransom note. If the retention factors are similar, it suggests that the marker was used in the ransom note.

3. The retention value is considered class evidence in this case. Class evidence is evidence that can be associated with a group of people or objects but not with a specific individual. In this case, the retention value can help determine which marker was used in the ransom note but cannot identify a specific individual as the perpetrator.