SPECTRAL INTERFERENCES BY POTASSIUM ON TH E DETERMINATION OF SELENIUMBY GRAPHITE-FURNACE AAS

It has been found that spectral interferences based on the molecular a bsorbance occurs at 196.0 nm of the selenium absorption line when a se lenium sample solution containing 100 mu g/ml of palladium in 3 mol/l sulfuric acid as a matrix modifier is measured by graphite furnace AAS equipped with a polarized d.c. Zeeman-effect background-correction sy stem. Spectral interferences were observed when both biological powder ed samples or the above-mentioned solution samples were measured. The degree of the spectral interferences depended on the amounts of potass ium coexisting in the samples. When the amounts of potassium coexisted at more than ca. 30 mu g, the molecular absorbance at 196.0 nm increa sed tenfold compared with the certified values for the certified refer ence materials. It was considered that the spectral interferences were caused by the molecular absorption, such as potassium sulfide or pota ssium chloride, because it was not observed when a sample solution con taining potassium nitrate was measured.