DEVELOPMENT OF A METHOD FOR DIRECT DETERM INATION OF SELENIUM BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY IN PLASMA, WHOLE-BLOOD, ERYTHROCYTES, PLATELETS AND LEUKOCYTES - DETERMINATION OF REFERENCE VALUES

The determination of the essential trace element selenium is becoming ever more important. In comparison with other trace elements, analysis of selenium using ETAAS is associated with complications. The reason for this is the low concentration of the element in the blood, the com plex nature of the matrix of the body, and the fact that the compounds of selenium are volatile at low temperatures. The Conventional determ ination of its concentration in serum or plasma does not accurately re flect the biochemical processes in the organism. A simple and rapid me thod for direct determination of selenium was therefore developed, whi ch also enables the detection of concentrations in whole blood, erythr ocytes. platelets, polymorphic and mononuclear leukocytes, as well as the concentration in plasma. Determination of the element is carried o ut using ETAAS (Zeeman 3030, Perkin-Elmer, Uberlingen). Maximum sensit ivity of the system is achieved, and interference avoided by using Zee man background compensation, an EDL lamp, graphite tubes with an integ rated platform, a palladium magnesium nitrate modifier, and direct cal ibration against reference material. The quality of the method is high , with a detection limit of 0.053 mu mol/l, and an interassay precisio n of 1.08 +/- 0.16 mu mol/l. Accuracy has been confirmed through the u se of reference materials, external quality controls and recovery anal ysis. The method does not require pre-mineralisation of the samples, a nd needs only few reagents and material. The selenium concentration me asured in a group of blood donors (n = 58; age 38.0 +/- 9.6 years) was 0.76 +/- 0.14 mu mol/l in plasma, 0.95 +/- 0.20 mu mol/l in whole blo od, and 0.00011 mu mol +/- 0.00004 mu mol/l in erythrocytes.