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Chemistry 440Forensic Science

Types of Illicit Drugs

Analysis of Illicit Drugs

Spot Tests for Drugs

Identification of Drugs by IR spectroscopy

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Qualitative analysis vs. quantitative analysis

Qualitative analysis simply deals with the identification

of the substance under consideration where as aquantitative analysis of the substance should provide the

actual percentage composition of the various

compounds that make up the substance.Drug Analysis-Spot Tests (Experiment 20), Lab

Manual pp 175-183,

Identification of Drugs by IR (Experiment 21)Identification of Drugs by GCMS (in-House)

Experiment : Salicylates in Blood Stream by Visible

Spectroscopy (Experiment 22, Part A and B)

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Addiction

Physical vs. Psychological addiction

Physical

causes withdrawl symptoms Alcohol, Narcotics, Depressants

Psychological addiction

Dopamine release Cocaine, PCP

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Classification of Drugs

Opiates/Narcotics

Reduce sensation sleep like state

morphine, heroin, codeine, fentanyl

Both physically and psychologically addictive

Stimulants

Stimulate sympathetic nervous system

high energy, euphoria

amphetamines, cocaine, nicotine

Psychologically addictive

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Classification of Drugs

Hallucinogens Alters perceptions, illusions

LSD (acid), PCP(angel dust), MDMA (Ecstacy),Mescaline (peyote cactus), Marijuana (THC),hallucinagenic mushrooms (psilocybin)

Most neither physical or psychological dependence

Depressants Depress CNS, drowsiness, slowed response

Barbiturates(Phenobarbital), Ethanol

Benzodiazepines (tricyclic anitdepressants) Valium(diazepam),Xanax(alprazolam)

Physically and psychologically addictive

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Analysis Sequence

Observations- Rock like, powdered, wet

Screening Test (Spot tests)- Used to categorize specimens to determine type of

substance present and to determine the bestprocedure to use for confirmation, color tests,microcrystalline tests

Chromatography (mixtures) (GC-MS)

Thin Layer Gas chromatography Mass spectrometry

Liquid chromatography Mass spectrometry (Dr.Huang)

Infrared Spectroscopy (pure) (IR experiment)

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Qualitative Analysis of Drugs

The chemistry section of a forensic laboratory

focuses on but not limited to the identification of

illegal drugs. This unit of the forensic laboratory

may also be asked to chemically identify arson

evidences, explosive analysis, blood alcohol

determination etc.

Spot Tests: Chemical analysis of illicit drugs

begin with a presumptive test more commonly

known as a spot test.

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Color tests

The suspected substance is treated with a particular

reagent that produces a color change indicating the

possible presence of a particular substance.

A positive coloration from a color test will always be

followed by additional tests to confirm the identity of the

substance. (IR, GC-MS etc)

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Color Test ReagentsMarquis Reagent: 2% formaldehyde in sulfuric

Acid (coloration with opiates and amphetamines)

Dillie Koppanyi Reagent: 1% Co(acetate)2 in

methanol followed by isopropyl amine.

(barbiturates)

Duquenois Levine Reagent: Soln. A: 2% vanillin

+ 1% acetaldehyde in ethanol, Soln. B: Conc. HCl

(marijuana)

Van Urk Reagent: 1% solution of p-

dimethylaminobenzladehyde in 10% con. HCl (LSD)

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Color Tests

Scott Test: 2% Co(SCN)2 in water followed by

SnCl2. (cocaine, procaine etc)

Meckes Reagent: Selenous acid

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Selecting an Analytical Technique

Considerations:

Organic v. Inorganic Chemicals

(anabundance of organic compounds areanalyzed as evidences)

Quantitative v. Qualitative

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Spectroscopy and ChromatographySpectroscopy (Spectrophotometry): Results

obtained from the interaction of matter with

electromagnetic radiation.

Infrared spectroscopy and UV-Vis

Spectrophotometry. (require pure material)

Chromatograpahy: Separation technique based on.

GC-MS: Simultaneous separation and analysis (can beconsidered as a qualitative and quantitative technique.

Most evidences collected will need purification

(Chromatography)

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Controlled Substances: Introduction to

Classification of Drugs

-A "collection" of organic compounds, the use of which

is regulated by the government.

It is often the case that a forensic chemist will be askedto qualitatively and quantitatively estimate the presence

and percentage composition of these substances in the

evidence collected near a drug related crime scene.

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Comprehensive Drug Abuse Prevention and

Control Act

In 1970 congress passed Public Law 91-513,

the Comprehensive Drug Abuse Prevention and

Control Act or more commonly known as the

Controlled Substance Act. Prior to the enactment

of this law, the nation had several patched-

together pieces of drug legislation which were

either repealed or superseded by the controlled

substance act.

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Drug-Free America Act

In 1986, the congress passed the Drug-Free

America Act (Public Law 99-570) which supersede

much of the 1970 Controlled Substance Act and

include greatly expanded penalties for the sale ,

manufacturing, possession, trafficking and

use(abuse) of the controlled substances.

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Designer Drugs

A term introduced in the 1986 legislation

anticipating the synthesis of future

analogs/modifications of controlledsubstances so that these new derivatives

become controlled substances even before

they are synthesized.

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Schedule I Drugs

High potency for abuse and no currently accepted

and approved medical use.

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Adrenaline and Noradrenaline

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Amphetamines

Stimulants

Produce intense euphoria

Many structural analogs of amphetamine havesubstantial medical benefits and are thus

present as active ingredients in prescription

medicines. (analytical methods must be very

specific)

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Morphine Based

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Serotonin Type

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Schedule II drugs

High potency for abuse but have currently

accepted and approved medical use with orwithout severe restrictions. Their abuse will

lead to severe physiological and physical

dependence.Opium, Cocaine, codeine, demerol, ritalin,

morphine, some barbiturates

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Metabolites of Cocaine

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Schedule III Drugs

Lower potency for abuse but have currently accepted

and approved medical use with or without sever

restrictions. Their abuse may lead to moderate or low

physical dependence.

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Thin Layer Chromatography

An example of solid liquid chromatography

Common adsorbents

Reverse Phase TLC

Visualization of spots: Visible colored spots, UV, iodine,

reagent sprays etc.

Comparison v. identification

Advantages of the method: Easily performed,

inexpensive, only microgram quantities of substance

required, etc

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Electrophoresis

Movement of charged molecules in presence of a

electric field gradient. (a coming attraction)

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Drugs to be tested

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Acknowledgment

The next several PowerPoint slides thatdescribe the theory and practice of IR

spectroscopy is an instructional

accompaniment to

Organic Chemistry, 5th Edition

L. G. Wade, Jr.

and was obtained from the following source

http://faculty.smu.edu/ebiehl/Wade12.ppt.

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Introduction to IR

Spectroscopy is an analytical technique

which helps determine structure.

It destroys little or no sample.

The amount of light absorbed by the

sample is measured as wavelength is

varied.

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Types of Spectroscopy

Infrared (IR) spectroscopy measures the bond

vibration frequencies in a molecule and is used

to determine the functional group.

Mass spectrometry (MS) fragments the moleculeand measures the masses.

Nuclear magnetic resonance (NMR)

spectroscopy detects signals from hydrogen

atoms and can be used to distinguish isomers.

Ultraviolet (UV) spectroscopy uses electron

transitions to determine bonding patterns. =>

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Electromagnetic Spectrum

Examples: X rays, microwaves, radio

waves, visible light, IR, and UV.

Frequency and wavelength are inversely

proportional.

c= , where cis the speed of light.

Energy per photon = h

, where h isPlancks constant. =>

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The Spectrum and Molecular Effects

=>

=>

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The IR Region Just below red in the visible region.

Wavelengths usually 2.5-25 m.

More common units are wavenumbers, orcm-1, the reciprocal of the wavelength in

centimeters.

Wavenumbers are proportional tofrequency and energy. =>

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Molecular Vibrations

Covalent bonds vibrate at only certain

allowable frequencies.

=>

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Stretching Frequencies

Frequency decreases with increasingatomic weight.

Frequency increases with increasing

bond energy. =>

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Vibrational Modes

Nonlinear molecule with n atoms usually has

3n - 6 fundamental vibrational modes.

=>

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Fingerprint of Molecule

Whole-molecule vibrations and bending

vibrations are also quantitized.

No two molecules will give exactly thesame IR spectrum (except enantiomers).

Simple stretching: 1600-3500 cm-1.

Complex vibrations: 600-1400 cm-1,called the fingerprint region.

=>

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IR-Active and Inactive

A polar bond is usually IR-active.

A nonpolar bond in a symmetrical

molecule will absorb weakly or not atall.

=>

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An Infrared Spectrometer

=>

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Carbon-Carbon

Bond Stretching Stronger bonds absorb at higher

frequencies:

C-C 1200 cm

-1

C=C 1660 cm-1

CC 2200 cm-1 (weak or absent if internal)

Conjugation lowers the frequency: isolated C=C 1640-1680 cm-1

conjugated C=C 1620-1640 cm-1

aromatic C=C approx. 1600 cm-1 =>

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Carbon-Hydrogen Stretching

Bonds with more s character absorb at a

higher frequency.

sp3 C-H, just below 3000 cm-1 (to the right)

sp2 C-H, just above 3000 cm-1 (to the left)

sp C-H, at 3300 cm-1

=>

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An Alkane IR Spectrum

=>

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An Alkene IR Spectrum

=>

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An Alkyne IR Spectrum

=>

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O-H and N-H Stretching

Both of these occur around 3300 cm-1, but

they look different.

Alcohol O-H, broad with rounded tip.

Secondary amine (R2NH), broad with one

sharp spike.

Primary amine (RNH2), broad with two sharp

spikes. No signal for a tertiary amine (R3N) =>

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An Alcohol IR

Spectrum

=>

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An Amine

IR Spectrum

=>

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Carbonyl Stretching

The C=O bond of simple ketones,

aldehydes, and carboxylic acids absorb

around 1710 cm-1. Usually, its the strongest IR signal.

Carboxylic acids will have O-H also.

Aldehydes have two C-H signals around2700 and 2800 cm-1.

=>

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A Ketone

IR Spectrum

=>

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An Aldehyde

IR Spectrum

=>

O H St t h f

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O-H Stretch of a

Carboxylic AcidThis O-H absorbs broadly, 2500-3500 cm-1,

due to strong hydrogen bonding.

=>

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Variations in

C=O Absorption Conjugation of C=O with C=C lowers thestretching frequency to ~1680 cm-1.

The C=O group of an amide absorbs at aneven lower frequency, 1640-1680 cm-1.

The C=O of an ester absorbs at a higher

frequency, ~1730-1740 cm

-1

. Carbonyl groups in small rings (5 Cs or

less) absorb at an even higher frequency.=>

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An Amide

IR Spectrum

=>

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Carbon - Nitrogen

Stretching C - N absorbs around 1200 cm-1.

C = N absorbs around 1660 cm-1 and is

much stronger than the C = Cabsorption in the same region.

C N absorbs strongly just above 2200

cm-1. The alkyne C C signal is muchweaker and is just below2200 cm-1 .

=>

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A Nitrile

IR Spectrum

=>

S f IR

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Summary of IR

Absorptions

=>=>

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Strengths and Limitations

IR alone cannot determine a structure.

Some signals may be ambiguous.

The functional group is usually indicated. The absence of a signal is definite proof

that the functional group is absent.

Correspondence with a known samplesIR spectrum confirms the identity of the

compound. =>

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Recording IR spectra

Neat: (the sample is placed directly in the path of

the IR beam, good for liquids and gases).

KBr pellet: (The solid sample is pressed into athin pellet with KBr and that pellet is placed in

the path of the IR beam)

Solution: The sample is dissolved in a solvent and the

IR spectrum of the solution is recorded)