COCAINE-LACED LOCKS TELL HAIRY TALES

Forensic scientists and toxicologists can read a history of chronic drug
use from a person's hair. Unlike urine and blood, which carry remnants of
recent drug use, hair preserves those clues from the moment it grows out of
a person's head.

One problem limits its usefulness as legal evidence, however. Current
analytical methods can't tell for sure how a drug such as cocaine made its
way into a strand of hair. The person in question could have ingested it
or just happened to be in the room when other people were smoking crack
cocaine. Vapors can coat the outside of the hair shaft and show up in a
laboratory test.

Scientists at the National Institute of Standards and Technology in
Gaithersburg, Md., are testing a new method that may solve this problem.
Instead of rinsing the hair with liquid solvents, as labs do now, they
dissolve cocaine out of hair with supercritical carbon dioxide (Science
News: 8/16/97, p. 108).

Their preliminary results, which appear in the Jan. 1 ANALYTICAL CHEMISTRY,
show that pure carbon dioxide removes cocaine only from the surface, but a
mixture of carbon dioxide, water, and the organic chemical triethylamine
removes drug traces bonded inside the hair shaft.

The water and triethylamine molecules "kick off the cocaine" from its
binding sites in hair, says study coauthor Janet F. Morrison, now at
Trinity College in Hartford, Conn. The method can be tuned to extract only
what the researcher wants.

Cocaine can penetrate hair in other ways, too. Perspiration on a person's
scalp, for example, might absorb cocaine vapors and then bind inside the
hair. Morrison and her coworkers are now treating hair samples with "fake
sweat" to test that possibility. - C.W.