Flame photometric detection of some transition metals. II. Enhancement of selectivity

Abstract

A flame photometric detector was used in single-channel and in differential dual-channel modes to characterize and control its selectivity for various transition elements against a hydrocarbon background. The experiments included gas-chromatographable compounds of Cr, Mn, Fe, Co, Ni, Ru, Re, and Os. Single-channel dispersive modes brought only modest gains in selectivity vis-a-vis the non-dispersive (no optical filter) mode. In dual-channel differential modes, however, metal–carbon selectivities could be improved by factors of one to two orders of magnitude. The highest still measurable selectivity ratios are now in excess of 107. The differential dual-channel operation of the detector also made it possible to increase the selectivity of one hetero-element vis-a-vis another; and to distinguish between two hetero-elements, by oppositely directed peaks, in a (spectrally suppressed) matrix of carbon compounds. Metal–metal selectivities could be improved by factors of one to three orders of magnitude over the best dispersive single-channel modes.