Separation of Selenium Forms and Their Determination Using Polyvinyl Formaldehyde Thiourea Sorbent

A polymer sorbent obtained by cocondensation of polyvinyl alcohol, formaldehyde, and thiourea (PVF-TU) is proposed for the concentration of Se(IV) and Se(VI) from aqueous solutions. The sorbent quantitatively extracts Se(IV) from 1–2 M HCl and Se(VI) at pH 3–6 in static mode (degree of recovery >98%). The time to achieve sorption equilibrium does not exceed 10 min. The sorption capacity of PVF-TU determined from horizontal sections of sorption isotherms is 50 μmol/g for Se(IV) and 25 μmol/g for Se(VI). The sorbent, containing Se(IV) and Se(VI) on the surface, dissolves in 5 mL of 2–4 M HNO3 at 90°C. With 100 mL of sample and 5 mL of desorbent solution, the concentration factor is 20. The developed procedure was used to determine the Se(IV) and Se(VI) content in bottled mineral waters using inductively coupled plasma atomic emission spectrometry and mass spectrometry.