Nitro gen Phosphorus Detector (NPD)

The nitrogen–phosphorus detector (NPD) is also known as thermionic specific detector (TSD) is a detector commonly used with gas chromatography, in which thermal energy is used to ionize an analyte. It is a type of flame thermionic detector (FTD), the other being the alkali flame-ionization detector (AFID also known as AFD).

With this method, nitrogen and phosphorus can be selectively detected with a sensitivity that is 10⁴ times greater than that for carbon