Drugs of abuse are typically measured by:

• A. Thin-layer chromatography
• B. Liquid-liquid chromatography
• C. Gas chromatography
• D. Steric exclusion chromatography

Answer: (C)

The main idea is the need for precise separation and definite identification of drugs in a complex toxicology sample. Gas chromatography is ideal for this because many abused drugs and their metabolites can be volatilized or derivatized so they can be carried through a narrow capillary column, where they separate into sharp, well-resolved peaks. When GC is paired with a detector like mass spectrometry, you not only separate the compounds but also obtain a unique mass signature that confirms exactly which drug is present and in what amount. This combination provides both high sensitivity and high specificity, which is why GC (especially GC-MS) is the standard for confirmatory drug-of-abuse testing. In contrast, thin-layer chromatography offers only basic, less sensitive separation; steroid exclusion chromatography is meant for macromolecules like polymers, not small drug molecules; and a term like liquid-liquid chromatography isn’t a typical primary method for routine drug analysis, making GC the best choice here.