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10.7 Notes. Toxicologists & Drug Analysis. Objectives. Describe techniques that forensics toxicologists use to isolate and identify drugs and poisons. Screening Tests. Use TLC, GC, Immunoassay Immunoassay – very different Based on specific drug antibody reactions - PowerPoint PPT Presentation

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  • Toxicologists & Drug Analysis

  • Describe techniques that forensics toxicologists use to isolate and identify drugs and poisons.Objectives

  • Use TLC, GC, ImmunoassayImmunoassay very differentBased on specific drug antibody reactionsAbility to detect small concentrationsBest for detecting marijuanaScreening Tests

  • GC/MSOne step test of unequaled sensitivity and specificityDrug testing not related to criminal matters

    Confirmation Tests

  • Drugs remain inBloodstream 24 hoursUrine 72 hoursTested in Private labs, typical for workplace screeningsHair nourished by blood flowing through capillaries near rootDrugs diffuse through capillary walls and become permanently entrapped in hairs protein structureDrugs location becomes historical marker for delineating drug intakeDrugs in Hair

  • Group of poisonsArsenic, Bismuth, Antimony, Mercury, ThalliumReinsch TestDissolve body fluid or tissue in hydrochloric acid solution then insert copper strip to solutionAppearance of silver or dark coating on copper indicates presence of heavy metalConfirm with inorganic analysisHeavy Metals

  • One of the most common poisonsPrimarily absorbed by red blood cellsCombines with hemoglobin to form carboxyhemoglobinNot enough hemoglobin left to carry oxygen to tissuesCauses asphyxiationCarbon Monoxide

  • Spectrophotometric visible spectrumGC liberates CO from bloodCalculate percent saturationGreater than 50-60% = fatalFatal levels can be lower when in combination with depressants2 Basic Methods for Detection of CO

  • High levels of carbon monoxide in blood indicate that victim breathed in products of fire and was alive when fire beganLow levels = dead before fire startedCould have been placed there to destroy evidenceArson Victim

  • Interpreting results is the most difficult choreBlood concentration levels can be used to estimate pharmacological effects of drugsSignificance of findings

  • Before drawing conclusions, toxicologists must consider other factors age, physical condition, drug history, toleranceProlonged use can make an individual less responsive to drugs effectsAdditive or synergistic effects provided by interaction of 2 or more drugsSignificance of findings

  • Concentration in urine is poor indicator because formed outside circulatory system and drug levels can build up over long periods of timeDrug can be found in urine 1-3 days after taken and long after other effects have disappearedBest used to corroborate other findings

  • 1970s, LAPD developed and tested clinical and psychophysical examinations that police officers could use to identify and differentiate between types of drug impairmentEvolved into national programStandardized methodsNot a substitute for toxicology testingDrug Recognition experts (DRE)

  • What is the difference between a screening test and a confirmation test?What are the three screening tests most widely used for forensic toxicology? What is the confirmation test of choice?Which of the following is not classified as a heavy metal?LeadArsenicMercuryThalliumExplain how inhaling carbon monoxide can cause death.Name at least three factors in addition to blood concentration levels that must be considered before drawing conclusions about a subjects drug induced behaviors.Why is the concentration of a drug present in urine a poor indicator of how extensively an individuals behavior or state is influenced by the drug?10.7 Questions