Novel thiol-functionalized covalent organic framework-enabled ICP-MS measurement of ultra-trace metals in complex matrices

Abstract

The measurement of ultra-trace levels of heavy metals in complex matrices is of great concern and challenge in life and environmental science. Herein, a novel thiol-functionalized covalent organic framework (COF) was prepared, and quantitative preconcentration of trace heavy metals in environmental water samples was achieved. The material was synthesized by a two-step reaction, including a Schiff base reaction between 1,3,5-triformylphloroglucinol (Tp) and 2,5-divinyl-p-phenylenediamine (DvPa) to form a preliminary COF (TpDvPa), and a thiol–ene “click” reaction between 1,2-ethanedithiol and the vinyl groups of TpDvPa to produce thiol-functionalized TpDvPa (TpDvPa-S-SH). By packing the material into a home-made SPE micro-column, and hyphenating the micro-column with inductively coupled plasma mass spectrometry (ICP-MS), trace levels of Co²⁺, Ni²⁺ and Cd²⁺ in environmental waters could be successfully preconcentrated and measured, with limits of detection of 1.46, 1.38 and 0.10 ng L⁻¹, respectively. The precisions were all less than 2.7%, with linear ranges extending from 5 to 1000 ng L⁻¹. The proposed method was validated by the analysis of the certified reference material (GBW08608), and measurement of Co²⁺, Ni²⁺ and Cd²⁺ in tap water, reservoir water, effluent of a wastewater treatment plant and sea water, confirming the accuracy and feasibility of the method.