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MEETING NEWS
Chasing down marijuana’s DNA profile
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Forensic scientists collect DNA profiles from marijuana to track its illegal origins.
illegal growers, distributors, and drug traffickers. What is new about the AFLP method, says Coyle, is that even though scientists routinely use chemical or DNA analysis to identify marijuana (Cannabis sativa L), “No methods allow for indi-
HEATHER COYLE, DEPT. OF PUBLIC SAFETY
DNA analysis has become invaluable for helping the “long arm of the law” nab criminals, but forensic scientists Heather Miller Coyle, Joselle Germano-Presby, and colleagues at the Connecticut State Forensic Science Laboratory would like to add a “green thumb” to that arm. Coyle and Germano-Presby are using amplified fragment length polymorphism (AFLP) to create DNA profiles of marijuana plants, which could link plants to
of Forensic Sciences
vidualizing a sample to say it is from this source and only this source—that is what we are working on,” she says. Marijuana, particularly female plants, contains high levels of the psychoactive compound tetrahydrocannabinol (THC). To get a plant as potent as possible, growers take cuttings from a high-THC plant and directly root them into soil to produce offspring. These cloned plants have identical DNA, which makes them easy to trace back to a particular batch or crop. Similarly, DNA taken from marijuana seeds can be linked back to a particular field or distributor. To identify plants, AFLP bands are converted to peak profiles using a software program, and the DNA profiles are compared for a match. Germano-Presby is currently working on developing a nationwide AFLP marijuana DNA database.
SPME versus ED for drug analysis Howard Harris and colleagues at the University of New Haven are using solid-phase microextraction (SPME) and extraction in a drop (ED) to provide forensic scientists and authorities with a faster analysis of complex street drugs. SPME is already used as an analysis tool in arson cases, but ED is relatively new to forensic scientists. “Both are popular extraction methods because of their potential of removing compounds
of interest from a complex matrix quickly and with some selectivity,” says Harris. To compare the methods, Harris and colleagues used each to investigate a cough and cold elixir containing 12.5 mg phenyl propanolamine, 2 mg brompheniramine maleate, and 10 mg dextromethorphan. All were diluted with an equal volume of buffer solution. After extraction, the ED drop was drawn back into the syringe, and the SPME fiber was with- SPME (left) and extracdrawn from the tion in a drop (ED) (right) vial. The fiber are used to give faster or the syringe drug analysis. with the drop was placed into the injector port of the GC/MS at 250 °C. ED provided useful results after only 10 s of extraction; SPME took ~30 s. After comparing the results, Harris believes that while both techniques have value, ED is simpler and requires no special equipment. “The technique should be attractive to chronically underfunded forensic labs,” he adds.
GOVERNMENT AND SOCIETY Low-tech chemical detector badge Emergency personnel arriving at the scene of a disastrous chemical spill or terrorist attack could receive early warning of a hazardous environment through a new chemical detector. Billed by its developers as low-tech, inexpensive, and 204 A
easy to use, the HazMat Smart Strip consists of reagent strips that change color instantly when they come into contact with eight different chemical classes of aerosols or liquids—chlorine, acids/bases (pH sensitive), fluoride,
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nerve agents, oxidizers, arsenic, sulfides, and cyanide (see box). “First responders” can wear this disposable device, designed in the form of an identification badge, on protective clothing or gear with a peel-and-stick adhesive strip or
HOWARD HARRIS, UNIV. OF NEW HAVEN
Wilder D. Smith reports from the 55th American Academy National Meeting—Chicago, Ill.
SAFETY SOLUTIONS
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Stylish and smart. A strip of reagents worn by first responders could help save lives.
clip. The device costs $15 and lasts up to 12 h after activated or until exposed to one of the substances. “This [test strip] encompasses the eight standard categories of toxic industrial chemicals likely to be out on roadways and railways, as well as those most likely to be used in a terrorist type of en-
Everything that’s detected by these strips can be analyzed with more sophisticated equipment, such as flame ionization or photoionization detectors, mass spectrometers, IR technology, atomic absorption systems, and the like, acknowledges Cris Aguirre, a firefighter and hazardous materials (haz-mat) technician with the Miami–Dade County Fire Department in Florida. “But there are a couple Sensitivity levels of reagent strips of things wrong with those inReagent Sensitivity struments,” he notes; they’re exChlorine 1 ppm pensive, they have to be calibratAcids/bases (pH) Above or below neutral Fluoride 20 ppm ed and maintained, their sensors Nerve agents In contact with nerve, blister, must be replaced, and extensive and choking agents training is required for their opOxidizers 1 ppm eration. Moreover, first responArsenic 0.5 ppb Hydrogen sulfide 5 ppm ders to a scene aren’t typically Cyanide 0.2 ppm going to be a haz-mat team, but rather fire suppression units and rescue personnel, he says. “The faster they can identify a substance, the vironment,” says Mike Lucey, manager faster we can get people with the proper of the National Technology Transfer equipment in there.” Center’s (NTTC) Emergency Response If the device really works as adverTechnology program. NTTC assisted the tised, “it’s certainly a step forward with product’s developer, Safety Solutions, Inc., in Boynton Beach, Fla., in commer- respect to our ability to make these kinds of detections,” says analytical cializing the device because “it fulfills a chemist David Walt at Tufts University. need for a lightweight chemical detector “You know not only that you’ve enthat’s easy to use and is an accurate indicountered something, but also which cator of harmful threats,” Lucey says.
substance it is, so you can make more intelligent and rapid decisions.” He warns, however, that any device will have some limitations. In particular, he raises concerns about potential false positives and negatives. For example, if the wearer came into contact with an insecticide such as malathion that had been sprayed on a field, would the nerve agent strip change color? Likewise, could there be false negatives due to sub-detection limit concentrations of exposure? “The user clearly needs to be informed about possible reasons for false positives and negatives to occur,” Walt says. According to Mike Reimer, vice president of Safety Solutions and an active haz-mat responder, the company has not had any false negatives. “We do have some false positives,” he acknowledges. “Roughly five industrial chemicals will give me false positives, but they’re few and far between, and because they are toxic, we want the strip to react with a positive indication.” Walt also points out that the device doesn’t detect all the substances one would like to detect—mustard agents that aren’t sulfide-based, for one, as well as the sedative gas used to neutralize the Chechen terrorists who took over the theater in Moscow last November. “I’m not surprised though, because it’s much more difficult to create the chemistry to do that rapidly and colorimetrically,” he says. Walt adds that while “it’s a useful, quick device that’s likely to provide a certain level of protection and additional level of comfort for first responders,” it’s only going to assist with a problem that already exists. “If there’s a problem that requires a first responder, presumably a bunch of people have already been exposed,” he notes. “That’s why continued research into sensors and detection systems that could be deployed widely to monitor these things continuously and anticipate or detect a release before it poses a threat is still necessary.” a –Kris Christen
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