Which instrumentation is commonly used for confirmatory testing of drugs in urine when high specificity is required?

Which instrumentation is commonly used for confirmatory testing of drugs in urine when high specificity is required?

• A. NMR spectroscopy
• B. Fluorescence spectrometry
• C. GC-MS
• D. ELISA

Answer: (C)

Confirmatory testing requires a method that uniquely identifies a drug in urine with very high specificity. Gas chromatography–mass spectrometry provides both a separation step and a definitive identification from the mass spectrum. The retention time from chromatography and the characteristic fragmentation pattern in MS allow matching to reference libraries, giving unambiguous results and accurate quantitation. This combination minimizes false positives and is why GC-MS is the standard instrument for confirmatory drug testing. Other techniques don’t offer the same level of specificity for definitive identification in routine confirmatory work. NMR is powerful but not practical here due to sensitivity, cost, and complexity for trace levels in urine. Fluorescence spectrometry can be sensitive but is not specific enough to confirm a particular drug, as many substances can produce similar signals. ELISA is a screening method designed for high throughput and initial detection, but it lacks definitive identification required for confirmation.

Confirmatory testing requires a method that uniquely identifies a drug in urine with very high specificity. Gas chromatography–mass spectrometry provides both a separation step and a definitive identification from the mass spectrum. The retention time from chromatography and the characteristic fragmentation pattern in MS allow matching to reference libraries, giving unambiguous results and accurate quantitation. This combination minimizes false positives and is why GC-MS is the standard instrument for confirmatory drug testing.

Other techniques don’t offer the same level of specificity for definitive identification in routine confirmatory work. NMR is powerful but not practical here due to sensitivity, cost, and complexity for trace levels in urine. Fluorescence spectrometry can be sensitive but is not specific enough to confirm a particular drug, as many substances can produce similar signals. ELISA is a screening method designed for high throughput and initial detection, but it lacks definitive identification required for confirmation.