Abstract: A net spectral intensity signal is derived from a comparison between the absolute spectral intensity of the signal interest and the intensity of a spectral continuum on which it rides. To derive the net signal, a pivotal refractor plate is mounted over the exit slit of a standard 1-meter monochromator. Pivoting of the plate produces a quick shift from the peak to its baseline signal. A programming circuit synchronizes the pivotal action with rotatably-indexed sample changer having a plural number of sample holders. The changer includes a fixed valve plate communicating with the capillary feed of a flame-emission burner and a rotatably-indexed plate having a plurality of ports each carrying a hypodermic needle for aspirating the test sample into the burner when the plate ports are mated. Repeated burnings are conducted for each sample both at the peak line and that of the spectral continuum and a multiplicity (300) of instantaneous digital signals are taken for each burning.