Flame photometric detector (FPD) is an excellent detector for compounds containing sulphur or phosphorus and also for the detection of heavy metals iron, lead and tin in organometallic compounds.
The carrier gas is hydrogen which is burnt in excess of air. When sulphur or phosphorus is absent, the flame does not emit much but in the presence of these elements there is luminous emission. Optical filters allow selection of either of the elements.
The detector consists of a hydrogen air burner and an attached photomultiplier tube. The photomultiplier is so arranged that only the upper portion of the flame is seen. The photo tube amplifies the current and registers it on a recorder. The detector allows estimation as low as a nanogram.