Magazine article Science News

Chemistry Catches Cocaine at Source

Magazine article Science News

Chemistry Catches Cocaine at Source

Article excerpt

Law-enforcement officials have a new weapon in the hunt for South American growers who cultivate coca plants for cocaine production. Scientists in the United States have devised a method for identifying the hidden chemical stamp of the narcotic's geographical origin.

The research team analyzed 200 sets of coca leaves of known origin provided by the Drug Enforcement Administration (DEA) to determine the signatures for five distinct coca-growing regions in the Andes. With this database, the team pinpointed the origin of their cocaine samples with 96 percent accuracy, as reported in the Nov. 16 NATURE. More recently, the researchers used the database to identify additional samples.

The method works because cocaine retains the chemical signature of the environment in which it grew, says James Ehleringer of the University of Utah in Salt Lake City. Various isotopes--atoms of the same element that have slightly different masses--of carbon and nitrogen find their way into coca plants in different proportions based on climatic conditions such as humidity, length of the dry season, and soil nutrients.

These isotopic ratios correctly identified the birthplace of 90 percent of the samples tested, says Ehleringer, who did the study with colleagues from both the University of Utah and a DEA laboratory in McLean, Va, Trace molecules, called alkaloids, provided the researchers with further distinctions among genetically different coca plants grown in various valleys, raising the accuracy further, Ehleringer says. …

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