Which detector is universal but typically less sensitive than mass spectrometry?

Which detector is universal but typically less sensitive than mass spectrometry?

• A. Ultraviolet–visible (UV-Vis) detector
• B. Diode array detector
• C. Refractive index detector
• D. Mass spectrometer

Answer: (C)

Universality in detectors means it responds to almost every solute, regardless of its specific chemistry. The refractive index detector does this by measuring changes in the refractive index of the mobile phase as each solute elutes. Because most compounds alter the mixture’s refractive index to some extent, it can detect a wide range of substances, making it universal. The trade-off is sensitivity: changes in refractive index with concentration are small, the signal is relatively weak, and baseline noise can be higher, so it’s not as sensitive as mass spectrometry. UV-Vis and diode array detectors only respond to compounds with UV-absorbing chromophores, so they’re not universal, while mass spectrometry is highly sensitive and selective but not universal in the same straightforward sense. Hence, the universal but typically less sensitive option is the refractive index detector.

Universality in detectors means it responds to almost every solute, regardless of its specific chemistry. The refractive index detector does this by measuring changes in the refractive index of the mobile phase as each solute elutes. Because most compounds alter the mixture’s refractive index to some extent, it can detect a wide range of substances, making it universal. The trade-off is sensitivity: changes in refractive index with concentration are small, the signal is relatively weak, and baseline noise can be higher, so it’s not as sensitive as mass spectrometry. UV-Vis and diode array detectors only respond to compounds with UV-absorbing chromophores, so they’re not universal, while mass spectrometry is highly sensitive and selective but not universal in the same straightforward sense. Hence, the universal but typically less sensitive option is the refractive index detector.