Nitrogen–phosphorus detector

The nitrogen - phosphorus detector ( nitrogen phosphorus detector, NPD, even PND) is one of the selective detectors. Detected compounds containing nitrogen and phosphorus, respectively, or can have an odd number of electrons. The structure is similar to the flame ionization detector ( FID).

The NPD, the sample is passed through a hydrogen / air plasma without causing hydrocarbons to be ionized to a great extent. Above the nozzle of a heated ceramic bead (usually made of rubidium or cesium silicate). Alkali metal ions on the ceramic bead and a suitably selected temperature to selectively enable the ionization of nitrogen or phosphorus compounds. It passes a current which is proportional to the amount of ions generated.

• Detector (chromatography )