Download Chapter 7 - Drugs

Chapter 7
Drugs
Chapter 7 - Drugs (and Crime)
A drug is a natural or synthetic substance designed to affect the subject
psychologically or physiologically.
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.
“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.
Controlled Substances Act
Schedule I—high potential for abuse; no currently accepted medical use
in the U.S.; a lack of accepted safety for use under medical supervision
Examples: heroin (diacetylmorphine), LSD, ecstasy (MDMA)
Schedule II—high potential for abuse; a currently
accepted medical use with severe restrictions; abuse
may lead to severe psychological or physical
dependence
Examples: cocaine, morphine, marijuana, amphetamines (including
methamphetamines), PCP, Ritalin
Schedule III—lower potential for abuse than the drugs in I or II; a
currently accepted medical use in the U.S.; abuse may lead to
moderate physical dependence or high psychological dependence
Examples: intermediate-acting barbiturates, anabolic steroids, ketamine
Controlled Substances Act, continued
Schedule IV—low potential for abuse relative to drugs in III; a
currently accepted medical use in the U.S.; abuse may lead to
limited physical or psychological dependence relative to drugs
in III
Examples: stimulants and depressants including Valium, Xanax,
Librium, phenobarbital, Darvon
Schedule V—low potential for abuse relative to drugs in IV; currently
accepted medical use in the U.S.; abuse may lead to limited physical or
psychological dependence relative to drugs in IV
Examples: codeine found in low doses in cough medicines
Classes of drugs
Narcotics: analgesics, relieve pain by depressing central nervous
system activity; leads to physical dependence;
opium derivatives, such as morphine, heroin
Hallucinogens: Cause marked changes in thought processes,
perceptions, and mood
Includes marijuana, LSD, PCP, MDMA
Depressants:
Alcohol, barbiturates, tranquilizers, inhalants
Stimulants:
Amphetamines, cocaine, crack
Illegal or Illicit?
An illegal drug is a drug that is against the law to have, use, or
distribute.
An illicit drug is a legal drug used in an inappropriate or illegal way.
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
Drug evidence can be
collected in the form of:
®Powders
®Tablets
®Capsules
®Vegetable matter
®Liquids
®Pipes
®Cigarettes
®Cookers
®syringes
They contain active
drug ingredients as
well as inactive
substances or additives
(sugar, starch, quinine)
to increase quantity,
dilute potency, and
raise total value.
Drug Identification
2-step procedure:
1) Use screening tests to reduce the number of possibilities to a small and
manageable number.
2) Use more sophisticated tests to pinpoint and confirm the identity of the drug.
Screening or presumptive tests only tell that the drug is possibly present.
(Screening tests are easier, cheaper, and quicker to use.)
Confirmatory tests tell that the drug is positively present.
Screening or presumptive tests
Confirmatory tests
Spot or color tests
Spectrophotometry
Microcrystalline test—
• Ultraviolet (UV)
a reagent is added to sample on a microscopic
slide, producing a crystalline precipitate that is
unique for a certain drug; size and shape of
crystals are specific to drug type
Chromatography
• Visible
• Infrared (IR)
Mass spectrometry
Presumptive Color Tests
(not conclusive evidence – not allowed in court)
Marquis — 2% formaldehyde in sulfuric acid; turns purple in the
presence of most opium derivatives and orange-brown with
amphetamines/methamphetamine
Dille-Koppanyi — 1% cobalt acetate in methanol followed by 5%
isopropylamine in methanol; turns violet-blue in the presence of
barbiturates
Duquenois-Levine — Solution A 2% vanillin and 1% acetylaldehyde
in ethyl alcohol; Solution B concentrated HCl and Solution C
(chloroform); a purple color in the chloroform layer indicates the
presence of marijuana
Van Urk — turns a blue-purple in the presence of LSD
Scott test — color test for cocaine; Solution A turns blue; Solution B
will turn the blue color to clear pink then Solution C will make the
blue color reappear
Chromatography
A technique for separating mixtures into their individual components
Requires a comparison between known and unknown drugs so one must
have a tentative ID on drug type before analysis.
Complements the color and crystal tests.
Includes two phases—a mobile one that flows past a stationary one
The mixture interacts with the stationary phase and separates
Types of
Chromatography
Paper
Thin-layer (TLC)
Gas (GC)
Pyrolysis gas (PGC)
Liquid (LC)
High-performance liquid (HPLC) Column
Paper Chromatography
Stationary phase—paper
Mobile phase—a liquid solvent
Capillary action moves the mobile phase through
the stationary phase.
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
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).
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
Uses of Gas Chromatography
Not considered a confirmation of a controlled substance
Used as a separation tool for mass spectroscopy (MS) and infrared spectroscopy (IR)
Used to quantitatively measure the concentration of a sample. (In a courtroom, there is no real
requirement to know the concentration of a substance. It does not affect guilt or innocence.)
Confirmatory Tests: Spectroscopy
Spectroscopy—the interaction of
electromagnetic radiation with matter
Spectrophotometer—an instrument used
to measure and record the absorption of
light in the ultraviolet (UV) and infrared
(IR) regions of the electromagnetic (EM)
spectrum of a chemical substance
Components
Types
A radiation source
Ultraviolet, Visible, Infrared
A frequency selector
A sample holder
A detector to convert electromagnetic radiation into an electrical signal
A recorder to produce a record of the signal
Additional notes
UV range is not conclusive. It only establishes a probable identity
for the substance.
IR can specifically identify a substance, like a fingerprint
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
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.
In a mass spectrometer, a high-energy electron beam is directed at
sample molecules in a vacuum chamber. The electrons break apart the
sample molecules into many positive-charged fragments. No two
compounds fragment in the exactly the same way. These are sorted
and collected according to their mass-to-charge ratio by an oscillating
electric or magnetic field.
Mass Spectra
Each molecular species has its own unique mass spectrum.
IR Spectrophotometry and Mass Spectrometry
Both work well in identifying pure substances.
Mixtures are difficult to identify in both techniques.
Both are compared to a catalog of knowns.
People of Historical Significance
Arthur Jeffrey Dempster was born in Canada, but studied at and
received his PhD from the University of Chicago. He began teaching
physics there in 1916. In 1918, Dempster developed the first modern
mass spectrometer. His version was over 100 times more accurate than
previous ones and established the basic theory and design of mass
spectrometers that is still used to this day.
Francis William Aston was a British physicist who won the 1922
Nobel Prize in Chemistry for his work in the invention of the mass
spectrograph. He used a method of electromagnetic focusing to
separate substances. This enabled him to identify no fewer than 212
of the 287 naturally occurring elemental isotopes.