Determination of cadmium in high-salt-containing samples by high-throughput solid phase microextraction coupled with...

Marine cadmium (Cd²⁺) pollution is threatening environmental safety and human health. Highly efficient detection of Cd²⁺ in seawater and urine is essential. Herein, a simple graphene oxide/multi-walled carbon nanotubes (GO/MWCNTs) hydrogel based high-throughput solid-phase microextraction (SPME) array was developed and coupled with liquid electrode glow discharge microplasma-induced vapor generation (LEGD-μPIVG) atomic fluorescence spectrometry (AFS) for sensitive determination of Cd²⁺. The GO/MWCNTs-coated fiber efficiently preconcentrated and separated Cd²⁺ from alkali/alkaline earth metals, thus mitigating interference from high-salt-containing matrix and improving sensitivity. The online elution of Cd²⁺ was achieved by inserting fiber into LEGD-μPIVG chamber as an electrode and injecting eluent into coating directly, further simplifying analytical steps. Under optimized conditions, the established method exhibited good linearity ranging from 0.05 to 5 μg L^-1, with coefficients of determination of 0.991. The developed approach provides an enhancement factor of 43 and a limit of detection of 4 ng L^-1. The relative standard deviations of the fiber-to-fiber (n = 20) and batch-to-batch reproducibility (n = 12) were less than 8.3 %. The accuracy and practicability of the proposed method were validated by analysis of Cd²⁺ in certified reference materials (GBW08607, GBW(E)091031, and GBW(E)091032), seawater samples, and urine samples with satisfactory t-test results with the certified values at the 95 % confidence level.