CFC Toxicology & Drug Analysis 2 — Questions and Answers
Question 1: Which analytical technique is considered the gold standard for confirming the identity of an unknown drug in forensic toxicology?
- High-performance liquid chromatography (HPLC)
- Gas chromatography-mass spectrometry (GC-MS) (Correct answer)
- Enzyme-linked immunosorbent assay (ELISA)
- Thin-layer chromatography (TLC)
Correct answer: Gas chromatography-mass spectrometry (GC-MS)
GC-MS combines separation with definitive molecular identification and is universally accepted as the confirmatory gold standard in forensic drug analysis.
Question 2: A victim's blood sample shows elevated carboxyhemoglobin levels. What toxicant is most likely responsible?
- Cyanide
- Carbon monoxide (Correct answer)
- Hydrogen sulfide
- Methanol
Correct answer: Carbon monoxide
Carbon monoxide binds hemoglobin to form carboxyhemoglobin, and elevated levels (>10%) are diagnostic of CO exposure.
Question 3: In postmortem redistribution, drug concentrations in which specimen are most affected by site-dependent changes?
- Vitreous humor
- Urine
- Hair
- Central blood (cardiac) (Correct answer)
Correct answer: Central blood (cardiac)
Central blood from the heart and great vessels is most susceptible to postmortem redistribution due to proximity to drug-rich organs like the liver and lungs.
Question 4: Which enzyme immunoassay cross-reacts most problematically with over-the-counter cold medications to produce false-positive amphetamine screens?
- Ephedrine and pseudoephedrine (Correct answer)
- Acetaminophen
- Guaifenesin
- Dextromethorphan
Correct answer: Ephedrine and pseudoephedrine
Ephedrine and pseudoephedrine share structural similarity with amphetamines and frequently cause false-positive immunoassay screens for amphetamines.
Question 5: What is the primary metabolite of cocaine detected in urine drug screens?
- Norcocaine
- Benzoylecgonine (Correct answer)
- Ecgonine methyl ester
- Cocaethylene
Correct answer: Benzoylecgonine
Benzoylecgonine is the major urinary metabolite of cocaine, persisting 2–4 days after use and targeted by immunoassay screens.
Question 6: A forensic toxicologist discovers that a decedent's vitreous ethanol is significantly higher than their peripheral blood ethanol. What does this most likely indicate?
- Postmortem ethanol production by microbial fermentation in blood
- Active alcohol absorption at the time of death (Correct answer)
- Antemortem ethanol ingestion days prior
- Sample contamination during collection
Correct answer: Active alcohol absorption at the time of death
When vitreous ethanol exceeds blood ethanol, it suggests the decedent was in the absorption phase, with blood-alcohol still rising at the time of death.
Question 7: Which pharmacokinetic parameter describes the volume of fluid a drug appears to occupy in the body relative to plasma concentration?
- Half-life (t½)
- Volume of distribution (Vd) (Correct answer)
- Clearance (CL)
- Bioavailability (F)
Correct answer: Volume of distribution (Vd)
Volume of distribution (Vd) relates the total amount of drug in the body to its plasma concentration, reflecting tissue binding and distribution.
CFC Toxicology & Drug Analysis 2
Which analytical technique is considered the gold standard for confirming the identity of an unknown drug in forensic toxicology?