OPTIMIZATION OF SELENIUM DETERMINATION IN HUMAN-MILK AND WHOLE-BLOOD BY FLOW-INJECTION HYDRIDE ATOMIC-ABSORPTION SPECTROMETRY

A flow injection hydride atomic absorption spectrometric (FI-HAAS) met hod was developed for determining selenium in human milk and whole blo od after microwave digestion of the sample. The sample (2 mL human mil k or 0.25 mL blood) was introduced into the microwave vessel with 1.5 mt HNO3 and 0.25 mt H2O, and 300 W (4 min) and 600 W (4 min) were appl ied. The digestion was completed by heating to 140 degrees C (2-3 h). Se (VI) was reduced to Se (IV) with hydrochloric acid. The instrumenta l conditions for FI-HAAS (concentrations of reducing agent and carrier acid, flow rate of argon carrier gas, and sample volume injected) wer e optimized, The detection limit of the proposed method was 0.23 ng/mL (assay) or 115 pg Se (absolute) in biological samples (1.15 ng/mL mil k, 10.4 ng/mL blood). The precision values were 5.0% for milk and 4.0% for blood. The accuracy was evaluated with 2 reference materials, Nat ional Institute of Standards and Technology Non-Fat Milk Powder (found : 104.3 +/- 7.2 ng/g, certified: 110 +/- 10 ng/g) and Whole Blood Sero norm (found: 81 +/- 7.3 ng/mL, reference: 83 +/- 4 ng/mL). The results show the suitability of the method for selenium determination in huma n milk and whole blood. The method was applied to whole blood samples obtained from pregnant women and to human milk.