A total-burn spectrographic method has been applied to the determination of trace concentrations of silicon in plutonium. The sample is oxidized to plutonium dioxide, mixed with a germanium dioxide—graphite mixture containing tin internal standard, packed into cupped graphite electrodes, and burned to completion in a high-amperage dc arc. Plutonium spectral interference is avoided by using the less sensitive Si 2506.90-Å line. The lower limit of the determination is 25 ppm of silicon in plutonium. The precision of the method is estimated to be ±8% (coefficient of variation) at the 270-ppm level and ±14% at 40 ppm.
Some factors which affect the assay of vitamin A by the spectrographic method