Analyte noise in the flame photometric detector

As the concentration of analyte increases in the flame photometric detector (FPD), its observed noise changes from a predominantly fundamental to a predominantly multiplicative variety. This change-over occurs typically in the 10(-9) to 10(-8) g/s region, with the precise position apparently dependent on the nature of the analyte. In the multiplicative region, slow fluctuations can be seen appearing simultaneously on both channels of a dual-channel FPD. This suggests the possibility of suppressing such correlated noise episodes.