Which method is the reference method for ethanol measurement?

Which method is the reference method for ethanol measurement?

• A. Enzymatic method
• B. Gas chromatography (GLC)
• C. Immunoassay
• D. Spectrophotometry

Answer: (B)

Gas chromatography provides the highest specificity for ethanol because it separates ethanol from other volatile substances before detection, allowing precise identification and quantification. In practice, a sample is vaporized and carried through a column by an inert gas; ethanol has a characteristic retention time and is detected by a sensitive detector such as a flame ionization detector, often with an internal standard to improve accuracy. This combination of separation and robust quantitation makes GC the gold-standard method used to establish ethanol levels in clinical and forensic settings, providing minimal interference from other compounds that can skew results with simpler methods. Enzymatic methods rely on alcohol dehydrogenase to oxidize ethanol and generate a measurable change (often NADH), but they can be affected by other alcohols or substances in the sample and may not discriminate perfectly between similar compounds. Immunoassays use antibodies and can suffer from cross-reactivity, leading to over- or underestimation if related compounds are present. Spectrophotometric approaches, especially those tied to NADH production, share similar limitations with interference and lack the definitive separation that GC provides, making them less reliable as a reference standard.

Gas chromatography provides the highest specificity for ethanol because it separates ethanol from other volatile substances before detection, allowing precise identification and quantification. In practice, a sample is vaporized and carried through a column by an inert gas; ethanol has a characteristic retention time and is detected by a sensitive detector such as a flame ionization detector, often with an internal standard to improve accuracy. This combination of separation and robust quantitation makes GC the gold-standard method used to establish ethanol levels in clinical and forensic settings, providing minimal interference from other compounds that can skew results with simpler methods.

Enzymatic methods rely on alcohol dehydrogenase to oxidize ethanol and generate a measurable change (often NADH), but they can be affected by other alcohols or substances in the sample and may not discriminate perfectly between similar compounds. Immunoassays use antibodies and can suffer from cross-reactivity, leading to over- or underestimation if related compounds are present. Spectrophotometric approaches, especially those tied to NADH production, share similar limitations with interference and lack the definitive separation that GC provides, making them less reliable as a reference standard.