Speciation of selenium (IV, VI) in urine and serum of thyroid patients by ultrasound-assisted dispersive liquid-liquid microextraction

In-vitro speciation of inorganic selenium (SeIV and SeVI) in serum blood and urine of hyperthyroidism and hypothyroidism patients based on isopropyl 2-[(isopropoxycarbothiolyl) disulfanyl] ethane thioate (IICDET) as a complexing agent were studied by ultrasound-assisted dispersive liquid-liquid bio-microextraction procedure (USA-DLLMBE). In first stage, 100 μL (≈0.1 g) of hydrophobic ionic liquid of [C8MIM][PF6] mixed with IICDET ligand and 100 μL of acetone. Then, the mixture injected to 10 mL of human samples at pH=4. After shacking, the Se (IV) ions were complexed by IICDET and extracted to IL at pH=4 (R-S: ...Se). The IL phase was separated from sample by centrifuging and inorganic selenium (Se IV) in remained samples was determined by electro thermal atomic absorption spectrometry (ET-AAS) after back extraction of Se (IV). As speciation, the Se (VI) reduced to Se (IV) in acidic pH (HCl, 130OC) and the total Se(T-Se) was obtained at pH=4. Therefore, the Se (VI) was calculated by difference of T-Se and Se (IV). After optimized conditions, the enrichment factor (EF), Linear range and limit of detection (LOD) for inorganic Se (IV) were obtained 20.1, 0.75- 20 μg L-1 and 0.18 μg L-1 in serum and urine samples respectively. The results showed us, the concentration of selenium was decreased in thyroid patients as compared to healthy peoples. The validation of methodology was achieved by certified reference material (CRM) and ICP-MS.