Post on 26-Dec-2015
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Screening and ConfirmationScreening and Confirmation
Forensic Scientists determine the Forensic Scientists determine the identity of drugs using…identity of drugs using…
Screening Tests – Screening Tests – preliminary tests preliminary tests used to reduce the # of possible used to reduce the # of possible identities of an unknown substance identities of an unknown substance (color tests & microcrystalline tests)(color tests & microcrystalline tests)
Confirmation – Confirmation – a single test that a single test that specifically identifies a substance.specifically identifies a substance.
Qualitative vs. QuantitativeQualitative vs. Quantitative
Identification of drugs may be…Identification of drugs may be… Qualitative – Qualitative – descriptive (An descriptive (An
unknown sample may be determined unknown sample may be determined to contain heroin and quinine.)to contain heroin and quinine.)
Quantitative-Quantitative-amount (A sample may amount (A sample may be determined to contain 10 % be determined to contain 10 % heroin and 90% quinine)heroin and 90% quinine)
Color TestsColor Tests
When mixed with a When mixed with a certain reagent, a certain reagent, a drug can produce a drug can produce a characteristic colorcharacteristic color
Useful for field Useful for field investigatorsinvestigators
Screening tests onlyScreening tests only YouTube - Spray drug YouTube - Spray drug
test kit for Cocaine restest kit for Cocaine residue detectionidue detection
Heroin
Meth
Color TestsColor Tests
Marquis – heroin, morphine, opium Marquis – heroin, morphine, opium derivatives, amphetaminesderivatives, amphetamines
Dille-Koppanyi-barbituratesDille-Koppanyi-barbiturates Duquenois-Levine – marijuanaDuquenois-Levine – marijuana Van Urk – LSDVan Urk – LSD Scott test - cocaineScott test - cocaine
Microcrystalline TestsMicrocrystalline Tests
A test that A test that identifies a specific identifies a specific substance based substance based on the color and on the color and shape of crystals shape of crystals formed when the formed when the substance is mixed substance is mixed with specific with specific reagents.reagents.
Methamphetamine
ChromatographyChromatography
An analytical technique An analytical technique used to separate the used to separate the components of a components of a mixture for the mixture for the purpose of purpose of identification and identification and quantification.quantification.
Useful to forensic Useful to forensic scientists because scientists because drugs often come in drugs often come in the form of a mixturesthe form of a mixtures
ChromatographyChromatography
All types of chromatography include:All types of chromatography include: Stationary Phase Stationary Phase – a solid substance used – a solid substance used
to adsorb components of a mixture.to adsorb components of a mixture. Mobile Phase Mobile Phase – a liquid or gas that flows – a liquid or gas that flows
through the stationary phase. through the stationary phase. Components of a mixture are separated Components of a mixture are separated
based on the speed that they move based on the speed that they move through the stationary phase.through the stationary phase.
The speed of a substance depends on how The speed of a substance depends on how strongly it is attracted to the mobile and strongly it is attracted to the mobile and stationary phases.stationary phases.
Thin-Layer ChromatographyThin-Layer Chromatography
TLC uses a solid TLC uses a solid (silica gel or (silica gel or aluminum oxide) aluminum oxide) coated on a plastic coated on a plastic or glass plate.or glass plate.
The plate is The plate is immersed in a immersed in a liquid solventliquid solvent
YouTube - Thin LayYouTube - Thin Layer Chromatographyer Chromatography of Felt Tipped Pens of Felt Tipped Pens
Thin Layer ChromatographyThin Layer Chromatography
As the solvent As the solvent travels up the travels up the chromatogram, chromatogram, components of a components of a mixture travel at mixture travel at different speeds.different speeds.
Unknown Unknown substances can be substances can be compared to compared to reference samples.reference samples.
Gas ChromatographyGas Chromatography
GC – solid stationary GC – solid stationary phase/gaseous mobile phase/gaseous mobile phasephase
Complex mixtures can Complex mixtures can easily be analyzedeasily be analyzed
Quantitative results Quantitative results can be obtainedcan be obtained
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SpectrophotometrySpectrophotometry
UV, Visible, and Infrared Light can be UV, Visible, and Infrared Light can be used to analyze unknown substancesused to analyze unknown substances
Substances absorb, reflect, or Substances absorb, reflect, or transmit various wavelengths of transmit various wavelengths of light.light.
This property can be used to This property can be used to indentify or quantify unknown indentify or quantify unknown substances.substances.
UV-Visible SpectrophotometryUV-Visible Spectrophotometry
The absorption of UV or visible light The absorption of UV or visible light can be used to indentify or quantify can be used to indentify or quantify an unknown substancean unknown substance
Identification is not exact; other Identification is not exact; other substances can have similar substances can have similar absorption spectraabsorption spectra
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Infrared SpectrophotometryInfrared Spectrophotometry
Unknown substances can be Unknown substances can be analyzed by measuring the analyzed by measuring the absorption of infrared light.absorption of infrared light.
The absorption pattern is much more The absorption pattern is much more complex than UV.complex than UV.
Substances can be specifically Substances can be specifically identified by their IR spectrum (like a identified by their IR spectrum (like a fingerprint)fingerprint)
Mass Spectrometry
Often used as a detector for Gas Often used as a detector for Gas ChromatographyChromatography
A substance is bombarded with high-A substance is bombarded with high-energy electronsenergy electrons
This causes the substance to ionize.This causes the substance to ionize. The ions break up into smaller The ions break up into smaller
fragments.fragments. The fragments are separated by massThe fragments are separated by mass The fragmentation pattern is unique to The fragmentation pattern is unique to
each individual substanceeach individual substance