Xylenol Orange-Functionalized Halloysite Nanotubes as a Novel Adsorbent for Selective Solid-phase Extraction and Determination of Trace Noble Elements

Abstract

A novel method using xylenol orange-modified halloysite nanotubes as a solid-phase sorbent has been developed for the simultaneous preconcentration and separation of trace Au(III) and Pd(II) prior to their determination by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The experimental effects of pH, the amount of adsorbent, sample flow rate, sample volume, interfering ions, and the elution condition were investigated in detail. Au(III) and Pd(II) were retained on the column at pH 3, and eluted with 2.0 mL of 1.0 mol/L HCl + 2% CS(NH2)2 solution. Common interfering ions did not have any impact on the adsorption, separation, and determination. An enrichment factor of 150 was obtained. The maximum adsorption capacities of the adsorbent were 41.63 and 47.82 mg/g for Au(III) and Pd(II), respectively, under the optimum conditions. By the definition of IUPAC, the detection limits (3σ) of this method for Au(III) and Pd(II) were 0.31 and 0.27 ng/mL, and the relative standard deviations (RSDs) were 2.7 and 3.2%, respectively (n = 8). This newly developed method was verified by certified reference materials, and has been successfully applied to the determination of trace Au(III) and Pd(II) in mine samples with satisfactory results. It can be confidently predicted that the method can be used for the determination trace Au(III) and Pd(II) in other real samples because of its high selectivity, sensitivity, and reproducibility.