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Drugs
Drugs
Drugs and Crime
A drug is a natural or synthetic substance designed to affect the subject
psychologically or physiologically.
“Controlled substances” are drugs that are restricted by law.
The Controlled Substances Act is a law that was enacted in 1970; it lists
illegal drugs, their categories, and penalties for possession, sale, or
use.
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Drugs
Controlled Substances Act
Schedule I—high potential for abuse; no currently accepted medical use in the U.S.
Examples: heroin (diacetylmorphine), LSD, marijuana, ecstasy (MDMA)
Schedule II—high potential for abuse; currently accepted medical use with severe restrictions;
Examples: cocaine, morphine, amphetamines (including methamphetamines), PCP, Ritalin
Schedule III—lower potential for abuse than the drugs in I or II; currently accepted medical use
Examples: intermediate-acting barbiturates, anabolic steroids, ketamine, codeine
Schedule IV—low potential for abuse relative to drugs in III; currently accepted medical use
Examples: stimulants and depressants including Valium, Xanax, Librium, phenobarbital
Schedule V—low potential for abuse; currently accepted medical use in the U.S.;
Examples: over-the-counter medications
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Drugs
® Stimulants: elevate a person’s mood temporarily, relieve some
symptoms of depression, usually not physically addictive but can
cause psychological dependence. Examples: cocaine, and
methamphetamine.
® Depressants: relieve anxiety, nervousness and restlessness; highly
addictives; sudden withdrawal can be fatal. Examples: barbiturates,
alcohol, diazepam (valium), quaaludes.
® Hallucinogens: cause auditory and visual hallucinations. Examples:
marijuana, LSD, PCP, mescaline (peyote), psilocybin (mushrooms)
® Narcotics: sleep-inducing, central nervous system depressants;
derived from the opium poppy. Examples: opium, morphine,
heroin, methadone, codeine, oxycodone
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Drugs
Human Components Used for Drug Analysis
Blood
Liver tissue
Urine
Brain tissue
Hair
Kidney tissue
Gastric contents
Spleen tissue
Bile
Vitreous humor of the eye
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Drugs
Physicians’ Desk Reference
PDR—A Physicians’ Desk Reference is used to identify manufactured
pills, tablets, and capsules. It is updated each year. This can
sometimes be a quick and easy identifier of the legally made drugs
that may be found at a scene. The reference book gives a picture of
the drug and states whether it is prescription, over-the-counter, or a
controlled substance; it gives more detailed information about the
drug as well.
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Drugs
® Screening Tests: add one or more chemical reagents to a
suspected drug and observe a color change. Ex: marijuana turns
purple, cocaine turns turquoise. Screening tests are not used to
confirm the presence of a specific drug because there could be
many drugs that give similar positive reactions.
® Separation Tests: Most illicit drugs are diluted with other
substances. Gas chromatography can separate the pure drug from
the cutting agents (sugars, powders, etc.)
® Confirmation Tests: Mass spectrometry confirms specific drugs
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Drugs
Drug Identification, continued
Screening or presumptive tests only tell that the drug is possibly present.
Confirmatory tests tell that the drug is positively present.
(Screening tests are easier, cheaper, and quicker to use.)
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Drugs
Chromatography
A technique for separating mixtures into their components
Includes two phases—a mobile one that flows past a stationary one
The mixture interacts with the stationary phase and separates
Types:
Paper
Thin-layer (TLC)
Gas (GC)
Pyrolysis gas (PGC)
Liquid (LC)
High-performance liquid (HPLC)
Column
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Drugs
Paper Chromatography
Stationary phase—paper
Mobile phase—a liquid solvent
Capillary action moves the mobile
phase through the stationary phase.
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Drugs
Thin-layer Chromatography
Stationary phase—a thin layer of
coating (usually alumina
or silica) on a sheet of plastic or
glass
Mobile phase—a liquid solvent
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Drugs
Retention Factor (Rf)
This is a number that represents how
far a compound travels in a
particular solvent.
It is determined by measuring the
distance the compound traveled
and dividing it by the distance the
solvent traveled.
If the Rf value for an unknown
compound is close to or the same
as that for the known compound,
the two compounds are likely
similar or identical (a match).
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Drugs
Gas Chromatography
Phases
Stationary—a solid or a
viscous liquid that lines a tube
or column
Mobile—an inert gas like
nitrogen or helium
Analysis
Shows a peak that is
proportional to the quantity of
the substance present
Uses retention time instead of Rf for
the qualitative analysis
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Drugs
Confirmatory Tests: Spectroscopy
Spectroscopy—the interaction of electromagnetic radiation with
matter
Spectrophotometer—an instrument used to measure and record
the absorption spectrum of a chemical substance
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Drugs
Infrared Spectrometry
Material absorbs energy in the near-IR region of the electromagnetic
spectrum
Compares the IR light beam before and after it passes through a
transparent sample
Result—an absorption or transmittance spectrum
Gives a unique view of the substance; like a fingerprint
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Drugs
Mass Spectrometry
Gas chromatography has one major drawback: It does not give a
specific identification. Mass spectrometry cannot separate mixtures. By
combining the two (GC-MS), constituents of mixtures can be
specifically identified.
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Drugs
Mass Spectra
Each molecular species has its own unique mass spectrum.
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