Imidazole functionalized organic monoliths for capillary microextraction of Co(II), Ni(II) and Cd(II) from urine prior to on-line ICP-MS detection

Monoliths composed of poly(1-vinylimidazole-ethylene glycol dimethacrylate), referred to as poly(VI-EGDMA), were modified with imidazole groups and used in capillary microextraction (CME) of trace levels of Co(II), Ni(II) and Cd(II) ions from human urine samples. The effects of sample pH, sample flow rate, sample volume, elution conditions and potentially interfering ions were investigated. Under the optimized conditions, the limits of detection (3σ) are 0.6 ng L−1 for Co(II), 6.4 ng L−1 for Ni(II) and 0.7 ng L−1 for Cd(II), with the relative standard deviations of 1.8 (Co), 4.2 (Ni) and 2.2% (Cd). A Certified Reference Material (ZK018–2, lyophilized human urine) was analyzed to validate the method, and the values found were in good agreement with the certified ones. The method was successfully applied to the analysis of trace Co, Ni and Cd in human urine samples, and the recoveries for spiked samples were in the range from 89% to 105%. The one-step preparation of monolithic material in our perception is an attractive feature for this material which also excels by good extraction performance in that it possesses abundant adsorption sites, good stability and a long lifetime.