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Drugs. Drug Analysis. General Principles. First test should be a visual examination naked eye low-power microscope especially important with plant materials & powders that do not appear to be uniform determine weight or volume of sample

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Drug analysis


Drug analysis

Drug Analysis

General principles

General Principles

  • First test should be a visual examination

    • naked eye

    • low-power microscope

      • especially important with plant materials & powders that do not appear to be uniform

      • determine weight or volume of sample

  • Examinations should proceed from general to the specific

    • each test should help narrow the number of possible substances that the sample could be

General principles1

General Principles

  • Analytical schemes and individual tests should conform to those already in general practice

General principles2

General Principles

  • When ever possible, at least one test should be specific for the drug in question

    • confirmatory test should be of a different type than those procedures used in the presumptive & separation phases of the examination

      • confirmatory tests

        • IR, GC-MS

      • presumptive or screening tests

        • “spot”tests, TLC

General principles3

General Principles

  • Try to conserve the drugs present as evidence

    • would allow for reanalysis

  • If the sample is too small to do a complete analysis

    • perform non-destructive tests before destructive tests

General principles4

General Principles

  • Tests should do double duty when possible

    • GC can be used for quantitative analysis as well as qualitative analysis

Scheme of analysis

Scheme of Analysis

  • Preliminary visual examination of all samples

  • Weigh all samples

  • Select representative samples (if appropriate)

  • Screening tests (usually spot)

  • Separation tests

  • confirmatory tests

Scheme of analysis1

Scheme of Analysis

  • Quantitative analysis if appropriate

  • Other tests if appropriate

Preliminary examination

Preliminary Examination

  • If there are a large number of samples with similar packaging segregate the samples into groups

  • Determine if the mixture is homogeneous

  • See if crystals of a drug have been coated onto plant material (microscope)

    • PCP is often coated onto marijuana or parsley

  • Hygroscopic materials such as cocaine tend to aggregate & become discolored

Screening tests

Screening Tests

  • Primary function to eliminate some drugs from consideration & indicate the identity of a drug

  • Categories

    • spot tests

    • microscopic tests

    • spectroscopic tests

Spot tests color tests

Spot Tests (Color Tests)

  • Often done on a spot plate or sometimes in a test tube

  • Normally destroy the sample

  • No spot test is specific for a particular drug

    • negative test is a good indicator for the absence of the controlled substances that respond positively to it

  • Diluents may interfere with some spot tests

    • especially concentrated sulfuric acid

Spot tests

Spot Tests

  • Marquis

    • 2% formaldehyde in sulfuric acid

      • turns purple in the presence of most opium derivatives

      • becomes orange-brown with amphetamines & methamphetamines

Spot tests1

Spot Tests

  • Dillie-Koppanyi

    • 1% cobalt acetate in methanol followed by 5% isopropylamine in methanol

      • turns violet-blue in the presence of most barbiturates

Spot tests2

Spot Tests

  • Duquenois-Levine

    • Reagent A: 2% vanillin & 1% acetaldehyde in ethanol

    • Reagent B: concentrated hydrochloric acid

    • Reagent C: chloroform

      • solutions are added sequentially to vegetation

        • purple color appears in the chloroform layer for marijuana

Spot tests3

Spot Tests

  • Van Urk

    • 1% solution of p-dimethlaminobenzaldehyde in 10% concentrated hydrochloric acid and ethanol

      • turns purple in the presence of LSD

  • Difficult to conduct in field

    • LSD is present in very small amounts in illicit preparations

Spot tests4

Spot Tests

  • Scott Test (cocaine)

    • solution A: 2% cobalt thiocayanate dissolve in water and glycerin (1:1)

    • solution B: concentrated hydrochloric acid

    • solution C: chloroform

      • powdered cocaine turns solution A blue

      • color turns pink on adding solution B

      • blue color appears in the chloroform layer on adding solution C

Microscopic tests

Microscopic Tests

  • Two Types

    • morphology tests

    • microcrystal tests

  • Morphology

    • most commonly used with plant matter such as marijuana

      • look for botanical features

Microcrystalline tests

Microcrystalline Tests

  • Involves dissolving the sample in a suitable solvent, filtering, and adding a precipitating agent to promote crystallization

  • The size & shape of the crystals are highly characteristic of the drug



  • TLC or GC

  • Comparison of Rf or retention-time values between questioned & known drugs

    • techniques accompanies and complements spot & crystal tests

Separation tests

Separation Tests

  • Tests that separate controlled substances from the matrix of diluents and other substances in a mixture

    • TLC, GC, HPLC

Confirmatory tests

Confirmatory Tests

  • A test that has the capability of identifying a drug after it has been presumptively identified by other techniques

    • individualization

    • generally spectroscopic

      • IR (method of choice in most forensic labs)

        • IR is unique for each compound (“fingerprint”)

        • substance should be as pure as possible

      • Mass Spectrometry

Methods of analysis narcotics heroine

Methods of Analysis---Narcotics (Heroine)

  • Color Tests

    • Marquis (purple); Froehde’s reagent (purple changing to olive green on standing) Mecke’s (yellow, turning to green on standing)

  • Microcrystalline Tests

    • platinum chloride, sodium acetate, mercuric chloride

Methods of analysis

Methods of Analysis

  • Separation---Heroine

    • easily separated from cutting agents by TLC

    • separated from quinine procaine, etc by a number of mobile phase systems

      • acetic acid:ethanol:water (30:60:10)

Analysis meth


  • Spot tests

    • Marquis (orange)

  • Confirmation

    • IR spectroscopy on free bases (liquids) or hydrochloride or sulfate salts

      • salts give better spectra

Analysis cocaine


  • Presumptive Tests

    • Spot Tests

      • Scott Test (blue;pink; blue)

    • TLC

    • Microcrystalline (gold chloride or lead iodide)

  • Quantitative analysis can be done by GC

  • Confirmatory Test

    • IR

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