Ultrasound-assisted dispersive solid-phase extraction of Ultratrace Fe(III) and Cr(III) from environmental waters using modified nanoporous MCM-41 as a novel adsorbent

A novel and highly selective method is presented for the preconcentration and determination of ultratrace Fe(III) and Cr(III) ions in environmental waters. The procedure integrates ultrasound-assisted dispersive solid-phase extraction (UA-DSPE) with flame atomic absorption spectrometric (FAAS) detection, using a newly engineered adsorbent. This material, acetylacetone-functionalized aminopropylated MCM-41 (acacAmpMCM-41), was specifically synthesized via covalent modification of mesoporous silica to impart tailored chelating affinity for trivalent metal cations. All parameters influencing extraction efficiency, including sample pH, adsorbent dosage, eluent composition, ultrasonication time, and sample volume, were systematically investigated and optimized. Under the established optimal conditions, quantitative adsorption was achieved within 20 min, followed by complete analyte recovery using 2.5 mL of 1.0 mol L −1 HNO 3 in a 10- desorption step. The method demonstrates excellent analytical performance, with low detection limits of 0.72 μg L −1 for Fe(III) and 0.44 μg L −1 for Cr(III), high precision (relative standard deviation