To achieve the best levels of sensitivity and specificity, gas chromatography should be coupled to which detector system?

• A. UV spectrophotometer
• B. Bichromatic spectrophotometer
• C. Mass spectrometer
• D. Fluorescence detector

Answer: (C)

Mass spectrometry provides the best combination of sensitivity and specificity when paired with gas chromatography. In GC-MS, compounds separated on the GC column are ionized and their mass-to-charge ratios are measured, producing a unique spectral fingerprint for each substance. This allows highly selective detection, especially when using selected ion monitoring, which boosts sensitivity by focusing on specific ions while minimizing background signals. It also enables confident identification through the characteristic fragmentation pattern, something optical detectors cannot offer.

Detectors based on UV absorption or fluorescence depend on whether a compound has the right chromophore or fluorophore, which limits universality and can lead to overlap and ambiguity in complex mixtures. A bichromatic spectrophotometer similarly relies on chosen wavelengths and lacks the molecular-level information that distinguishes closely related compounds. So while those detectors can be very useful for certain targets, they don’t provide the broad, confirmatory specificity that GC-MS does.