Determination of Trace Levels of Selenium in Biological Samples by Graphite Furnace Atomic Absorption Spectrometry with a Solid Sampling Technique. Application of Pre-Ashing Concentration Technique

Abstract

A highly sensitive and convenient analytical method for the direct determination of selenium in biological samples by GF-AAS with a solid sampling technique using a graphite miniature cup was established by using a Pd solution containing 3 mol/l sulfuric acid or a Pd solution containing 0.1 mol/l nitric acid as a matrix modifier in order to prevent the volatilization of selenium. The determination of μg/g levels of selenium in biological samples was performed using calibration curves prepared by a selenium standard solution containing 100 μg/ml of Pd in 3 mol/l sulfuric acid as the matrix modifier. On the other hand, the pre-ashing concentration technique, which was previously developed by us, was applied to the determination of 10 ng/g levels of selenium in biological samples. The analytes in biological samples were concentrated by decomposing the sample matrix with a conventional electrothermal muffle furnace at 600° C for 30 min, At the pre-ashing stage, a Pd solution containing 0.1 mol/l nitric acid was added, because the addition of the Pd solution containing sulfuric acid caused charring and coagulation of the samples. The concentration factor for selenium in biological samples was 10 to 40. The analytical results of several NIST biological certified reference materials obtained by the proposed method were in good agreement with the certified values. The detection limit of GF-AAS was 0.13 ng of selenium; therefore, 3.3 ng/g levels of selenium in biological samples is detectable by the proposed method.