QUENCHING IN THE FLAME PHOTOMETRIC DETECTOR

The conventional, roughly quadratic sulphur response mode in the flame photometric detector (FPD) is subject to severe quenching by co-eluting hydrocarbons. This interference is greatly reduced in a new, linear sulfur response mode, which tolerates an about twentyfold larger amount of quencher. Under these conditions, the response of a variety of elements is quenched to a similar extent as that of sulphur; i.e. the amount of quencher needed to halve response typically varies by a factor no greater than three between sulphur and any of the other five elements tested (Fe, Sn, P, Mn and Cr). It is therefore possible to speculate that linear sulfur is not quenched by a mechanism sui generis, but that it is simply subject to the same general quenching process(es) as other FPD analytes. The extent of quenching for all tested elements is largely independent of analyte concentration-provided the latter remains within linear range.