Selenium adsorption and speciation with Mg–FeCO3 layered double hydroxides loaded cellulose fibre

A novel adsorbent was developed by coating Mg–FeCO3 layered double hydroxides (LDHs) on cellulose fibre. The LDHs take up significant amount of selenite and selenate in a wide pH range with similar sorption capacities (pH 3.8–8.0 for selenite and pH 5.8–7.0 for selenate). A mini-column packed with Mg–FeCO3 LDHs layer coated cellulose fibre particles was incorporated into a sequential injection system for uptake of selenite at pH 6.0. The retained selenite was afterwards collected with 70 μL of 0.8%(m/v) NaOH as eluent, followed by hydride generation and atomic fluorescence spectrometric detection. Total inorganic selenium was adsorbed at pH 6.0 by the LDHs-cellulose fibre mini-column after selenate was pre-reduced to selenite by 2.0 mol L−1 HCl at 80 °C, and selenium speciation was performed by difference. With a sample volume of 1.0 mL, an enrichment factor of 13.3 was derived with a detection limit of 11 ng L−1 within a linear range of 0.04–4.0 μg L−1. A relative standard deviation (RSD) of 3.3% (0.5 μg L−1, n = 11) was achieved. The procedure was validated by analyzing selenium in a certified reference material GBW 10010 (rice), and speciation of inorganic selenium in natural water samples.