Nano-alumina coated with sodium dodecyl sulfate and modified with 4-(2-Pyridylazo) resorcinol for extraction of heavy metals in different matrixes

A green, novel and efficient solid phase extraction method based on the use of nano-alumina (nano-Al₂O₃) coated with sodium dodecyl sulfate (SDS) and modified with 4-(2-Pyridylazo) resorcinol (PAR) as a new adsorbent was developed for separation and preconcentration of trace amounts of Ni, Pb, Cu and Zn ions prior to determination by inductively coupled plasma-optical emission spectrometry (ICP-OES). Under the optimum conditions (eluent: HNO₃, 4.0 mL, 3.0 mol L⁻¹; adsorbent: 0.8 g of nano-Al₂O₃, 40 mg of SDS, 8.6 mg of PAR; and sample: pH 6, flow rate 2.0 mL min⁻¹), adsorption capacity of nano-Al₂O₃-SDS-PAR, enrichment factors and limits of detection for the analytes were 8.7–12.9 mg g⁻¹, 125–250, and 0.12–0.71 μg L⁻¹, respectively. The proposed method presented excellent repeatability with relative standard deviations less than 1.6% (n = 10), and calculated calibration curves gave good level of linearity with correlation coefficient values between 0.989 and 0.999. Finally, the feasibility of the method was evaluated by extraction and determination of Ni, Pb, Cu and Zn ions in rice seed, apple juice, coriander, lettuce and tap water samples.