Ultrasonic-aided dispersive solid-phase microextraction employing magnetic halloysite nano clay for simultaneous preconcentration of lead (II) and cadmium (II)

• Synthesis of magnetic halloysite nano clay Fe 3 O 4 @HNT via co-precipitation. • Investigation of influential parameters for DMSPE using fractional factorial design and central composite design. • Application of dispersive micro solid phase extraction for preconcentration DMSPE of Cd 2+ and Pb 2+ simultaneously. • The developed DSPME/ICP-OES method applicability for Cd 2+ and Pb 2+ monitoring in various water samples. Heavy metal poisoning of water by lead Pb(II) and cadmium Cd(II) is a severe environmental issue. A magnetic halloysite nano clay (Fe 3 O 4 @HNT) was synthesised for the simultaneous preconcentration of Cd(II) and Pb(II) using an ultrasound-assisted dispersive micro-solid phase extraction technique (US-DMSPE). Various characterisation techniques were employed to characterise the nanocomposite, confirming the nanostructure and chemical composition of Fe 3 O 4 @HNT. The transmission electron microscope (TEM) showed that the inner cavity of the tube was approximately 10–21 nm (with an average of 13.4 ± 3.4 nm), and the lengths are variable. In addition, the open-ended and inner cavity characteristics provided a passage and additional active sorption sites for the target analytes. Brunauer–Emmett–Teller (BET) confirmed the mesoporosity of the adsorbent, which corresponds with the inner diameter as confirmed by TEM. The preconcentration parameters were optimised using fractional factorial design (FrFD) and central composite design (CCD). Under the optimised experimental conditions, the detection limits were 0.037 and 0.054 µg/L, and the dynamic range was 0.1–400 µg/L for cadmium and lead, respectively. The method had good precision with RSD (<4.5 %) and R 2 (0.9987 for cadmium and 0.9975 for lead). This technique successfully determined lead and cadmium in water samples with excellent relative recovery in the 98.8 to 106 % range.