The contamination of the environment, particularly in the form of wastewater, is a significant issue that has arisen as a consequence of industrial processes and human activity. Furthermore, there has been a notable increase in heavy metal contamination in this type of environment in recent years, which has become a significant concern for different environmental agencies [1, 2]. These trace metals can enter the human body causing different health disorders [3]. For that reason the determination of these toxic metal ions in water and aquatic ecosystems is of great importance. To that end, a straightforward, sensitive and matrix effect free analytical method for simultaneous determination of Cd, Cr, Cu, Mn, Ni, Pb and Zn in wastewater samples by inductively coupled plasma optical emission spectrometry (ICP OES) has been developed. In order to eliminate potential interferences from the matrix and to increase the sensitivity of the method a dispersive liquid-liquid microextraction (DLLME) has been performed using a new ferrofluid as a magnetic extractant phase formed by a deep eutectic solvent (DES) and magnetic nanoparticles obtained from commercial toner powder. By utilizing this magnetic extractant phase, the need for centrifugation is eliminated, resulting in significant time and energy savings while making the method more environmentally friendly. Following the microextraction process, a back-extraction step with HCl was required to prevent the introduction of magnetic nanoparticles from the magnetic extractant phase into the ICP OES system. The main experimental factors affecting the DLLME procedure have been optimized using a multivariate analysis and under optimized conditions, the limits of detection (LODs) obtained with the proposed method are ranged from 0.12 to 3 µg L^-1. In addition, the trueness has been evaluated by recovery experiments in a real wastewater sample, being the recovery values within the range of 92-102 %.

Acknowledgements

The authors are grateful to the European Commission and Spanish Ministry of Science and Innovation (PID2021-126155OB-I00) and the Regional Government of Valencia (Spain) (CIPROM/2021/062, INVEST/2022/70) for the financial support. The authors are also grateful to the Spanish Ministry of Science and Innovation for granting the Spanish Network of Excellence in Sample Preparation (RED2022-134079-T).

References

[1] J. Sardans; F. Montes; J. Peñuelas, Spectrochimica Acta Part B, 2010, 65, 97-112.

[2] J. Wang; C. Chen; Biotechnology Advances, 2009, 27, 195-226.

[3] P.J. Harvey; H.K. Handley; M.P. Taylor, Environmental Science and Pollution Research, 2015, 22, 12276-1288.