Preconcentration of Cadmium from Wastewater Samples Using Zinc Oxide Nanoparticle-Based Dispersive Solid Phase Extraction (DSPE) with Flame Atomic Absorption Spectrometry (FAAS) Detection

Zinc oxide (ZnO) nanoparticles were synthesized for use in a dispersive solid phase extraction (DSPE) method aimed at preconcentrating cadmium (Cd) from wastewater samples. The combination of the ZnO nanoparticle-based DSPE method with flame atomic absorption spectrometry (FAAS) enabled sensitive and accurate determination of Cd at trace levels. The relevant parameters of the DSPE method, including buffer volume and pH (1.0 mL, pH 9.0), sample volume (40 mL), amount of nanoparticles (25 mg), mixing mode and period (vortex, 30 s), and eluent concentration and volume (5.0 M nitric acid, 100 µL), were optimized to increase the analyte signal-to-noise ratio. Next, the method’s performance was assessed, yielding a limit of detection of 0.4 µg/L, a limit of quantitation of 1.4 µg/L, and a dynamic range of 1.0–20 µg/L. The quantitation capability of the FAAS system was enhanced 31-fold with the developed preconcentration method when the quantitation limits of the developed ZnO nanoparticle-based DSPE–FAAS method and the FAAS system were compared. The accuracy of the developed method was checked using the spiked synthetic and domestic wastewater samples. The recovery results obtained (94.0–110.5%) via matrix-matching calibration showed that the developed ZnO nanoparticle-based DSPE–FAAS method was accurately applied to wastewater samples to determine their Cd content.