Fabrication of Functional Groups-Rich Monolith for Magnetic Field-Assisted In-Tube Solid Phase Microextraction of Inorganic Selenium Species in Water Samples Followed by Online Chromatographic Determination

Abstract

Efficient separation and enrichment is a crucial step in the analysis of Se(IV) and Se(VI). In the present study, for the first time, online monolith-based magnetic field-assisted in-tube solid phase microextraction (MFA/IT-SPME) was applied to capture inorganic selenium species in water samples. In this connection, porous monolith mingled with magnetic nanoparticles was synthesized in silica capillary and employed as microextraction column (MEC) of MFA/IT-SPME. After that, a magnetic coil utilized to perform variable magnetic fields in adsorption and desorption steps was twined on the MEC. Se(IV) was coordinated with o -phenylenediamine to form coordination compound which was infused to the MEC to be captured. Results evidenced that application of magnetic field during extraction procedure assisted the capture of Se(IV)-OPA complex with the enhancement of extraction efficiency from 83% to 97%. Under the optimized conditions, MFA/IT-SPME was online combined with HPLC equipped with diode array detector (DAD) to perform quantification of Se(IV) and Se(VI) in environmental water samples. Total inorganic Se was quantified after pre-reduction of Se(VI) to Se(IV) prior to applying established approach, and subtraction method was adopted to calculate Se(VI) and Se(IV) contents. The limit of detection for Se(IV) was as low as 0.012 μg/L. Reliability of suggested method was investigated by assaying Se(IV) and Se(VI) species in real-life waters with satisfactory recoveries (81.1%-116%) and repeatability (RSDs below 9%).