Operating Principle
Sample eluting from the GC column burns in a hydrogen-rich flame, where some species are reduced and excited, emitting photons when they relax. Bandpass filters allow photons unique to sulfur (394 nm) or phosphorus (526 nm) to reach a photomultiplier tube (PMT). The photons strike a photosensitive surface in the PMT, which ejects electrons, causing a cascade that is then recorded as a signal. As a result, the FPD is both selective and sensitive but has a more limited dynamic range and can be subject to PMT saturation. FPDs are considered mass-based detectors.
