Which is the most sensitive detector for spectrophotometry?

Which is the most sensitive detector for spectrophotometry?

• A. Photomultiplier
• B. Phototube
• C. Electron multiplier
• D. Photodiode array

Answer: (A)

Detector sensitivity in spectrophotometry comes from how effectively a device converts light into a signal and how much amplification it provides to that signal. The photomultiplier tube uses a photocathode to emit electrons when photons arrive, and these electrons are amplified through a cascade of dynodes, producing gains of millions to tens of millions. That enormous amplification makes even a single photon detectable above noise, giving the highest sensitivity. It also typically exhibits very low noise and fast, broad spectral response, which are ideal for detecting very weak light signals. A simple phototube lacks this internal amplification, so its signal is much smaller relative to noise and it’s far less sensitive. An electron multiplier by itself is an amplification stage and, without the complete photocathode-to-anode system, doesn’t reach the same level of sensitivity as a full photomultiplier. A photodiode array relies on solid-state diodes with much less gain, so while it offers rapid multi-wavelength detection and good linearity, its sensitivity at very low light levels is lower than that of a photomultiplier. So, for detecting the faintest light signals in spectrophotometry, the photomultiplier provides the best sensitivity.

Detector sensitivity in spectrophotometry comes from how effectively a device converts light into a signal and how much amplification it provides to that signal. The photomultiplier tube uses a photocathode to emit electrons when photons arrive, and these electrons are amplified through a cascade of dynodes, producing gains of millions to tens of millions. That enormous amplification makes even a single photon detectable above noise, giving the highest sensitivity. It also typically exhibits very low noise and fast, broad spectral response, which are ideal for detecting very weak light signals.

A simple phototube lacks this internal amplification, so its signal is much smaller relative to noise and it’s far less sensitive. An electron multiplier by itself is an amplification stage and, without the complete photocathode-to-anode system, doesn’t reach the same level of sensitivity as a full photomultiplier. A photodiode array relies on solid-state diodes with much less gain, so while it offers rapid multi-wavelength detection and good linearity, its sensitivity at very low light levels is lower than that of a photomultiplier.

So, for detecting the faintest light signals in spectrophotometry, the photomultiplier provides the best sensitivity.