Rapid and simple determination of selenium and other trace elements in very small blood samples by XRF

Selenium and other trace elements (Cu, Zn, Br, and Rb) were determined in very small (0.75 microL) human serum and mice whole blood samples, by an XRF method. Accurate results of elemental concentration were obtained without the need of exact volume measurement, because of the backscatter correction used. The XRF method is highly sensitive (M.D.L. = 0.06, 0.13, 0.09, 0.07, and 0.05 ppm for Se, Cu, Zn, Br, and Rb, respectively), rapid (counting time--100 s/sample), easy to perform and therefore suitable for routine trace element analyses. The results obtained are in good agreement with the values reported in the literature.