Synthesis of a novel magnetic nanomaterial for the development of a multielemental speciation method of lead, mercury, and vanadium via HPLC-ICP MS

Abstract

A new magnetic functionalized material based on graphene oxide magnetic nanoparticles named by us, M@GO-TS, was designed and characterized in order to develop a magnetic solid-phase extraction method (MSPE) to enrich inorganic and organic species of lead, mercury, and vanadium. A flow injection (FI) system was used to preconcentrate the metallic and organometallic species simultaneously, while the ultra-trace separation and determination of the selected species were achieved by high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICP MS). Therefore, preconcentration and separation/determination processes were automated and conducted separately. To the best of our knowledge, this is the first method combining an online MSPE and HPLC-ICP MS for multielemental speciation. Under the optimized conditions, the enrichment factor obtained for Pb^II, trimethyllead (TML), Hg^II, methylmercury (MetHg), and V^V was 27. The calculated LOD for all studied species were as follows: 5 ng L^-1, 20 ng L^-1, 2 ng L^-1, 10 ng L^-1, and 0.4 ng L^-1, respectively. The RSD values calculated with a solution containing 0.5 μg L^-1 of all species were between 2.5 and 4.5%. The developed method was validated by analyzing Certified Reference Materials TMDA 64.3 for total concentration and also by recovery analysis of the species in human urine from volunteers and a seawater sample collected in Málaga. The t statistical test showed no significant differences between the certified and found values for TMDA 64.3. All the recoveries obtained from spiked human urine and seawater samples were close to 100%. All samples were analyzed using external calibration. The developed method is sensitive and promising for routine monitoring of the selected species in environmental waters and biological samples.

Keywords: HPLC-ICP MS; Magnetic graphene oxide; Multielemental speciation; Solid-phase extraction.

Fig. 1

Scheme of the FI system used for preconcentration: (A) loading step and (B) elution step. Peristaltic pumps (P1 and P2), magnetic knotted reactor (MKR), waste (W), sample (S), and eluent (E) [22]

Fig. 2

Chromatogram of the selected species under optimum conditions. Y-axis signal intensity (c/s) and X-axis time (min). Total time of the chromatogram: 20 min. Monitored signals: (A) Hg²⁰², (B) Pb²⁰⁸, and (C) V⁵¹

Fig. 3

Response surfaces obtained for the optimization of eluent composition. Desirability function maximizes the response function (s/n) for all species: (A) desirability in front of EDTA and L-Cys concentration and (B) desirability in front of phosphoric acid and thiourea concentrations, respectively