*Article* **Multi-Element Analysis Based on an Automated On-Line Microcolumn Separation/Preconcentration System Using a Novel Sol-Gel Thiocyanatopropyl-Functionalized Silica Sorbent Prior to ICP-AES for Environmental Water Samples**

**Natalia Manousi <sup>1</sup> , Abuzar Kabir <sup>2</sup> , Kenneth G. Furton <sup>2</sup> , George A. Zachariadis <sup>1</sup> and Aristidis Anthemidis 1,\***

	- International Forensic Research Institute, Department of Chemistry and Biochemistry,
	- Florida International University, Miami, FL 33131, USA; akabir@fiu.edu (A.K.); furtonk@fiu.edu (K.G.F.)

**Citation:** Manousi, N.; Kabir, A.; Furton, K.G.; Zachariadis, G.A.; Anthemidis, A. Multi-Element Analysis Based on an Automated On-Line Microcolumn Separation/Preconcentration System Using a Novel Sol-Gel Thiocyanatopropyl-Functionalized Silica Sorbent Prior to ICP-AES for Environmental Water Samples. *Molecules* **2021**, *26*, 4461. https:// doi.org/10.3390/molecules26154461

Academic Editors: Victoria Samanidou, Irene Panderi and Pawel Pohl

Received: 6 July 2021 Accepted: 21 July 2021 Published: 24 July 2021

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**Abstract:** A sol-gel thiocyanatopropyl-functionalized silica sorbent was synthesized and employed for an automated on-line microcolumn preconcentration platform as a front-end to inductively coupled plasma atomic emission spectroscopy (ICP-AES) for the simultaneous determination of Cd(II), Pb(II), Cu(II), Cr(III), Co(II), Ni(II), Zn(II), Mn(II), Hg(II), and V(II). The developed system is based on an easy-to-repack microcolumn construction integrated into a flow injection manifold coupled directly to ICP-AES's nebulizer. After on-line extraction/preconcentration of the target analyte onto the surface of the sorbent, successive elution with 1.0 mol L−<sup>1</sup> HNO<sup>3</sup> was performed. All main chemical and hydrodynamic factors affecting the effectiveness of the system were thoroughly investigated and optimized. Under optimized experimental conditions, for 60 s preconcentration time, the enhancement factor achieved for the target analytes was between 31 to 53. The limits of detection varied in the range of 0.05 to 0.24 µg L−<sup>1</sup> , while the limits of quantification ranged from 0.17 to 0.79 µg L−<sup>1</sup> . The precision of the method was expressed in terms of relative standard deviation (RSD%) and was less than 7.9%. Furthermore, good method accuracy was observed by analyzing three certified reference materials. The proposed method was also successfully employed for the analysis of environmental water samples.

**Keywords:** automation; flow injection; inductively coupled plasma; sol-gel; solid-phase extraction; metals
