Synthesis and Characterization of a Silica/Tungsten(VI) Oxide and Its Performance for the On-Line Solid-Phase Extraction (SPE) of Nickel Ions from Aqueous Media with Determination by Flame Atomic Absorption Spectrometry (FAAS)

Abstract

The present paper describes a new analytical method exploiting a SiO₂/WO₃ mixed oxide as an adsorbent synthesized via sol-gel process for the preconcentration of Ni²⁺. This material was characterized by energy dispersive X-ray fluorescence spectroscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, analysis of the specific surface area by Brauner, Emmett and Telle multipoint method, the average pore size and pore volume by Barrett-Joyner-Halenda method, scanning electron microscopy, and electron dispersive spectroscopy. The mixed oxide presented high surface area (710.9 m² g⁻¹), average pore size of 35.1 Å, and average pore volume of 0.128 cm⁻³ g⁻¹. This material was used as the an adsorbent in an on-line procedure for pre-concentration of solid phase extraction, based on the adsorption of Ni²⁺ ions at pH 10.5 followed by elution with 1.0 mol L⁻¹ HNO₃ and determination by flame atomic absorption spectrometry. Under optimized conditions, a linear range from 10.0 to 170.0 µg L⁻¹, an enrichment factor of 38.8-fold, and limits of detection and quantification of 4.23 µg L⁻¹ and 14.11 µg L⁻¹ were obtained. The precision of method, estimated as percentage of relative standard deviation of ten replicates of 30.0, 90.0 and 150.0 µg L⁻¹ Ni²⁺ solutions, was lower than 4.10%. The method was employed for analysis of water samples and the accuracy was attested by addiction and recovery tests, with satisfactory recoveries (98.4–109.2%). Thus, the developed material can be successfully applied to water samples for monitoring of Ni²⁺ at very low levels without matrix influence.

Keywords:

• Flame atomic absorption spectrometry (FAAS)
• silica/tungsten(VI) oxide
• SiO2/WO3 mixed oxide
• solid-phase extraction (SPE)
• water samples

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that influenced the results reported in this paper

Additional information

Funding

The authors acknowledge the financial support and fellowships of Coordenação de Aperfeiçoamento de Nível Superior (CAPES) (Project Pró-Forenses 3353/2014 Grant 23038.007082/2014-03), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (Grant No 307432/2017-3), Fundação Araucária do Paraná (163/2014), SETI do Paraná, Instituto Nacional de Ciência e Tecnologia de Bioanalítica (INCT) (FAPESP Grant No 2014/50867-3 and CNPq Grant No 465389/2014-7), Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) and Instituto Nacional de Tecnologias Alternativas para Detecção, Avaliação Toxicológica e Remoção de Micropoluentes e Radioativos (INCT-DATREM).