Ligandless dispersive solid phase extraction of cobalt ion using magnetic graphene oxide as an adsorbent followed by its determination with electrothermal atomic absorption spectrometry

ABSTRACT

Ligandless dispersive solid phase extraction technique was used for preconcentration of cobalt ion (Co²⁺) followed by its determination using electrothermal atomic absorption spectrometry (ETAAS). Graphene oxide (GO) was synthesised from graphite by the Hummer method and chemically magnetised to synthesise of the magnetic graphene oxide (MGO). The synthesised MGO was characterised by the Fourier transform-infrared spectrophotometry (FT-IR), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) and then used as an adsorbent for solid phase extraction of Co²⁺. The main parameters affecting the extraction recovery of Co²⁺ including pH of sample solution, amounts of adsorbent, extraction time and type and concentration of desorption solvent were investigated and optimised. The calibration curve was plotted in the range of 0.08–1.2 µg L⁻¹ Co²⁺ with a correlation coefficient of 0.9987. The intra-day precision based on six replicate analysis of 0.2 µg L⁻¹ Co²⁺ was 3.8% and the limit of detection (LOD) was 0.023 µg L⁻¹ Co²⁺ (n = 5). Also, the adsorption isotherms and adsorption kinetics were investigated and based on the obtained results, the adsorption of Co²⁺ onto the MGO nanocomposite followed by both Langmuir and Freundlich isotherms with a maximum adsorption capacity of 114.9 mg g⁻¹ Co²⁺. The results of kinetic models also show that the adsorption of Co²⁺ followed by the pseudo second order kinetic model. The accuracy of the proposed method was successfully checked by the analysis of two certified reference materials including certified reference material-trace metals in drinking water (CRM-TMDW) and spinach leaves 1570a samples (Student t-test with 95% confidence limit, n = 5). Finally, the proposed rapid and efficient solid phase extraction technique was used for the determination of trace levels of Co²⁺ in the human saliva, urine and different real samples.

KEYWORDS:

• Magnetic graphene oxide
• dispersive solid phase extraction
• cobalt
• electrothermal atomic absorption spectrometry
• human saliva and urine samples
• adsorption isotherm
• adsorption kinetic

Acknowledgments

The authors wish to thank the University of Neyshabur for supporting of this project.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the university of neyshabur [14205].