Direct determination of selenium in whole blood by electrothermal atomic absorption spectrometry using W–Rh-coated platform and co-injection of Rh as thermal stabilizer

A W–Rh coating on the integrated platform of a transversely heated graphite atomizer (platform modifier) and a RhCl3 solution (analyte/matrix modifier) were combined for the direct determination of selenium in whole blood by electrothermal atomic absorption spectrometry. Samples were diluted 1+4 v/v with a mixture of 0.2% v/v HNO3 and 0.5% v/v Triton X-100. For the analysis, 12 μl of the resulting sample plus 6 μl of the Rh solution were delivered into the transversely heated graphite atomizer (THGA) platform modified with W–Rh. The combined use of Rh solution with the W–Rh coating was decisive in increasing the maximum pyrolysis temperature of blood selenium up to 1300 °C. Use of W–Rh as a platform modifier increased the tube useful lifetime up to 200% when compared to an untreated platform using a conventional [Pd+Mg(NO3)2] modifier. The accuracy and precision of the method proposed were verified by analyzing serum certified reference material (Seronorm™) and 20 whole blood samples using Pd/Mg(NO3)2 modifier in untreated platforms; no statistical differences were found between methods by applying the t-test at the 95% level.