Legal Tender or Criminal Evidence

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Note: This project involves testing for a controlled substance, and therefore you are required to work with an authorized forensic scientist under strict guidelines and complete additional forms for the prescreening of your project and approval by a scientific review committee authorized by your state or regional science fair prior to the start of your research. Additionally, this project requires the use of materials and equipment found in a forensic chemistry laboratory.


To determine if traces of cocaine residue are present on a random sampling of currency acquired from a local financial institution.


Statistics indicate that cocaine use has increased in recent years. The drug is often taken by inhaling the powdery substance into the nose through a straw or rolled up currency. Studies by the Federal Bureau of Investigation and recent national news reports have indicated that a large percentage of currency in circulation today contains traces of cocaine. Testing a random sampling of currency may uncover traces of this drug and may indicate usage of the drug in a particular geographic location.

Materials Needed

  • Ten $1, $5, $10, $20, $50, and $100 bills with recent issue date
  • Sterile latex gloves
  • Apron
  • Safety goggles
  • 60 50-ml test tubes
  • Labeling stickers
  • 1,000 ml methanol
  • Beaker
  • 2 pairs of tweezers
  • 60 rubber stoppers for test tubes
  • Test tube racks
  • Paper towels
  • Fume hood
  • One 10-microliter syringe
  • Access to a gas chromatograph mass spectrometer


Sixty bills, 10 each in the denominations of $1, $5, $10, $20, $50, and $100, will be obtained from the same source (local financial institution) and will all have a recent issue date (to ensure that any traces of cocaine found are from recent usage). The bills will be washed in test tubes containing methanol to remove any residue from the bills. Once the samples have been washed and the methanol has been allowed to evaporate from the tube, the remaining residue will be tested with the use of a gas chromatograph mass spectrometer for the purpose of identifying traces of cocaine on the currency.


  1. Put on the apron, latex gloves, and safety goggles.
  2. Place a labeling sticker with a sample number on each test tube and stopper. Each tube should be labeled with an increasing number, using the bill denomination as the first number and the sample number as the second identifier. Record the corresponding sample number next to the appropriate bill serial number in a log book.
  3. Measure 30 milliliters of methanol into a beaker and pour into one test tube.
  4. Roll one bill sample into a cylindrical shape.
  5. Submerge the bill into the test tube using a pair of tweezers.
  6. Securely place a stopper on the test tube.
  7. Shake the test tube for approximately one minute.
  8. Place the test tube in the test tube rack.
  9. Remove stopper from the test tube.
  10. Using both pairs of tweezers, carefully remove the bill. Hold the bill directly abovethe test tube and gently squeeze with the tweezers to allow more of the methanol to drip back into the test tube.
  11. Unroll the bill and lay it flat on a paper towel to dry.
  12. Repeat steps 3–11 for each bill to be sampled.
  13. Leave all test tubes uncovered under the fume hood and allow the methanol to evaporate to approximately 1–2 milliliters of solution. Be sure to monitor the samples regularly to check the evaporation progress.
  14. Once samples have evaporated sufficiently, use a 10-microliter syringe to inject approximately 1 microliter of solution from a sample into the gas chromatograph mass spectrometer. Rinse the syringe with methanol to clean it.
  15. The gas chromatograph separates the compounds and then sends the separated compounds to the mass spectrometer, where they are identified by mass.
  16. A computer program will identify the molecular weight and search for the three molecular weights that combine to form cocaine, namely, 82, 182, and 303.
  17. Analyze each reading to see if the 3 molecular weights appear simultaneously, thereby providing positive evidence of cocaine.
  18. Repeat steps 14–17 for each bill sample and record your data results.


  1. Did any of the bills test positive for traces of cocaine? What percentage of the bills, if any, contained traces of cocaine?
  2. Did lower or higher denominations of bills studied have a higher percentage of cocaine residue?
  3. What factors—such as the source of the currency sampled, the denomination of the bills sampled, and the length of time the currency has been in circulation—might affect the end results of this study?
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