AnalyticForensic Toxicology Ch 31

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Analytic/ForensicToxicology Ch 31

• By
• Amber Smith

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Introduction

• Analytic ToxicologyInvolves application of the
  tools of analytic chemistry to the qualitative or
  quantitative estimations of chemicals that may
  exert adverse effects on living organisms
• Forensic ToxicologyThe use of toxicology for
  purposes of the law

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Analytic Toxicology

• Encompasses all chemical substances
• Gases
• Volatile Substances
• Corrosive Agents
• Metals
• Anions and Nonmetals
• Nonvolatile Organic Substances
• Miscellaneous

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Gases

• Most simply measured by Gas Chromatography

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Volatile Substances

• Generally consists of liquids of a variety of
  chemical types
• Measured by Gas-Liquid Chromatography for
  separation and quantitation

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Corrosives

• Includes mineral acids and bases
• Detected by clinical chemical techniques

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Metals

• Encountered as occupational and environmental
  hazards
• Separation procedures involve the destruction of
  the organic matrix by chemical or thermal
  oxidation

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Toxic Anions and Nonmetals

• May be trapped in combination with a stable
  cation
• Can be separated by dialysis and are detected by
  Chromatagraphic procedures and Ion-Specific
  Electrodes

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Nonvolatile Organic Substances

• The largest group of substances
• Includes prescribed and illegal drugs,
  pesticides, natural products, pollutants, and
  industrial compounds
• Detected through immunoassay procedures

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Miscellaneous

• Includes venoms and other toxic mixtures of
  proteins
• Detects most practically by immunoassay procedures

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Role in General Toxicology

• Monitoring dosage forms or solutions for
  stability throughout the course of an experiment
• Important in establishing the bioavailability of
  a compound under study

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Role in Forensic Toxicology

• Postmortem Investigations
• Cause of death in poisoning cases
• Presence of intoxicating of ethanol in car
  accidents
• Carbon Monoxide detection
• Provide data for substance abuse
• Assist in cause of death for a court of law

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Toxicologic Investigation of a Poison Death

• 3 steps
• Obtaining case history and suitable specimens
• Toxicologic analyses
• Interpretation of Analytic findings

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Case History and Specimens

• Collect facts
• Gross autopsy findings
• Drugs available to the decedent
• Interval between the onset of symptoms and death
• Analyses performed
• Analyzed Specimens

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Toxicologic Analyses

• Factors to consider
• Amount of specimen available
• Nature of the poison sought
• Possible biotransformation of the poison

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Toxicologic Analyses

• Organs Analyzed
• Gastrointestinal contents
• Urine
• Liver

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Toxicologic Analyses

• Problems
• Hydrolysis, oxidation or reduction of proteins,
  nucleic acids, or lipids that may generate
  compounds that interfere with identification

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Toxicologic Analyses

• Testing
• Ferric chloride, perchloric, and nitric adic
  color test for phenothiazine drugs and
  immunoassays for the detection of amphetamines,
  benzodiazepines, and opiates in the urine
• GC/MC or HPLC is most widely used for most drug
  identification

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Interpretation of Analytic Results

• Provides answers
• Route of Administration
• Dosage and if of toxicant present is enough
  to cause death or alter action enough to cause
  death
• Tests on blood, tissue, and plasma
• Results are often used to corroborate
  investigative findings

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Criminal Poisoning of the Living

• GC/MS HPLC tests are used for 2 types of
  poisoning
• Administration of drugs to incapacitate victims
  of kidnapping, robbery, or sexual assault
• Poisoning as a form of child abuse deliberate
  administration of toxic or injurious substances
  to a child, usually by a parent of other caregiver

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Forensic Urine Drug Testing

• Urine is the only specimen analyzed and is only
  tested for a limited number of drugs
• Testing consists of immunoassays
• Sample is checked for adulteration by checking
  the pH, creatine, specific gravity, and for any
  unusual color or smell

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Human Performance Testing

• Tests for ethanol and chemicals in blood, breath,
  or other specimens that may modify performance of
  behavior
• Common application for DUI and DUID
• Alcohol related accidents are responsible for
  55-65 of fatalities in drivers

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Courtroom Testimony

• Toxicologist is an expert witness providing an
  objective testimony and opinion
• Objectiveinvolves desciption of his or her
  analytic methods and findings
• Opinionhow the person interprets the results

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Role in Clinical Toxicology

• Used to identify the nature of the toxic exposure
  and measure the amount of the toxic substance
  that has been absorbed
• Also monitoring the amount of the toxic agent
  remaining in circulation or measuring what is
  excreted

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Role in Therapeutic Monitoring

• Determine individual variability to drugs by
• Rate and extent of drug absorption
• Distribution and binding in body tissues and
  fluids
• Rate of metabolism and excretion
• Pathologic conditions
• Interaction with other drugs

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Role in Biologic Monitoring

• Monitor workers directly for exposure
• Exposures are to a mixture of compounds
• Must be able to measure minute of the
  compound
• Measure changes of normal metabolites induced by
  xenobiotics

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References

• Klaassen, C.D. 2001. Casarett Doulls
  Toxicology The Basic Science of Poisons. New
  York, NY. McGraw-Hill Companies Inc.

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Questions

• What are 4 of the 7 substances measured by an
  Analytic Toxicologist?
• What are the 3 steps used for toxicologic
  investigation of a poison death?