Green Approach for the Simultaneous Determination of Nickel and Cobalt Using Magnetic Cellulose and Flow-Injection with Flame Atomic Absorption Spectrometry.

A green analytical method was developed for the simultaneous, rather than sequential, determination of Ni and Co using magnetic cellulose as a sorbent for preconcentration, coupled to high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) via a segmented flow injection device. Magnetic cellulose, synthesized by coprecipitation of iron oxide, proved to be an efficient, biodegradable sorbent for rapid metal uptake, providing preconcentration factors of 27.0 for Ni and 28.2 for Co under optimized conditions. Isotherm modeling and pH-dependent sorption behavior support an electrostatic ion-exchange mechanism governed by the oxygenated functional groups of cellulose, thereby enabling efficient and reversible metal recovery. Coupling magnetic cellulose microextraction with the flow injection system minimized sample dispersion, enhancing signal stability and enabling low characteristic concentrations (Ni 0.78µgL⁻¹ and Co 1.36µgL⁻¹), high extraction efficiency (>92%), high precision (RSD < 4.3%), and low detection limits (0.3µgL⁻¹ for Ni and 1.9µgL⁻¹ for Co). Recoveries of 96–103% in fortified real water samples confirmed its applicability under realistic conditions. The green metrics assessment (AGREE, AGREEprep, BAGI) further confirmed the environmental compatibility, practicality, and sustainability. Overall, this work introduces a novel, eco-friendly, robust, and sensitive strategy for the reliable simultaneous monitoring of Ni and Co in environmental water samples.