Optimization of a new methodology for trace determination of elements in biological fluids: Application for speciation of inorganic selenium in children’s blood

Abstract The continuous sample drop flow microextraction (CSDFME) joined with the iridium-modified tube graphite furnace atomic absorption spectrometry (GFAAS) has been developed as a highly sensitive technique for the speciation of selenium in blood samples. In this method 32.0 μl carbon tetrachloride is transferred to the bottom of a conical sample cup. Then the 5.0 ml of aqueous solution transforms to fine droplets while passing through the organic solvent. At this stage, Se(IV)-APDC hydrophobic complex is extracted into the organic solvent. After extraction, the conical sample cup is transferred to the GFAAS and 20 μl of extraction solvent was injected into the graphite tube by the aim of autosampler. Under the optimum conditions, the calibration graph was linear in the range of 0.06–3.0 μg l −1 with detection limit of 0.02 μg l −1 . The enrichment factor and enhancement factor were 106 and 91, respectively. Repeatability (intra–day) and reproducibility (inter–day) of method based on seven replicate measurements of 2.5 μg l −1 of selenium were 3.7% and 4.2%, respectively. Total inorganic Se(IV, VΙ) was measured after reduction of Se(VΙ) with gentle boiling in 5 M HCl medium for 50 min and adjusting pH to 3, and the concentration of Se(VΙ) was calculated by subtracting the Se(IV) concentration from the total selenium concentration.