Online solid sampling platform using multi-wall carbon nanotube assisted matrix solid phase dispersion for mercury speciation in fish by HPLC-ICP-MS

Abstract

The integrity of chemical species throughout the analytical procedure and sample throughput are usually two serious impediments in elemental speciation. In this work, a simple solid sampling platform using multi-wall carbon nanotubes (MWCNTs) assisted matrix solid phase dispersion (MSPD) was constructed for online coupling to high performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for the high accuracy and sample throughput mercury speciation in fish samples. Owing to the large surface area and excellent mechanical strength of MWCNTs, which facilitate a sufficient dispersion of a sample matrix and diffusion of the eluent into the mixture of solid support and fish samples, a fast, efficient and online extraction of mercury species was achieved. Compared to the conventional MSPD and other sample pretreatment methods, the proposed method has several advantages including the integration of extraction, clean-up, separation and determination into one single step to achieve a high sample throughput, eliminating the need for derivatization of the Hg species and/or subsequent purification steps, reduced usage of solid supports, minimized contamination and mild operation conditions. The limits of detection of 9.9 ng g⁻¹ and 8.4 ng g⁻¹ were obtained for Hg²⁺ and CH₃Hg⁺, respectively, based on 1 mg of fish sample. The accuracy of the proposed method was validated by analyzing two certified reference materials. The proposed method was applied for two fresh fish samples for Hg speciation.