Abstract: A new alkali-ceramic Cs source used in the thermionic detector for gas chromatography was made . Acomparison between the sensitivity of rubidium bead and that of caesium bead for alkali-compounds of eguivalent density is made. The response of the bead to different concentrations of Cs and the effect of the heating current are also discussed.

Key words: Thermionic detector for GC, Caesium source, Response property