The need of analytical methods for absolute quantitative protein analysis spurred research on new developments in recent years. In this paper, a sensitive and selective method based on mercury labeled magnetic immunoassay and inductively coupled plasma mass spectrometry (ICP-MS) detection was proposed for the quantification of carcinoembryonic antigen (CEA) in real human serum samples. Size exclusion chromatography (SEC) combined with ICP-MS was applied for the separation and detection of secondary antibody labeled with mercury and excess mercury. After a complete sandwich-type immunoreaction among primary antibody, CEA and secondary antibody labeled with mercury on magnetic nanoparticles (MNPs), the concentration of CEA was determined by microconcentric nebulizer (MCN)-ICP-MS analysis of mercury ion released from secondary antibody with an acid-dissolution (pH 1.0) step. With consumption of only 50 μL sample solution, the established method presented a limit of detection of 0.041 ng mL−1 for CEA, with the relative standard deviation (RSD) of 5.2% (c = 8 ng mL−1, n = 7). The response for CEA was linear over a dynamic range from 0.1 to 50 ng mL−1. The analytical results of CEA in three different human serum samples obtained by the proposed method are in good agreement with that obtained by the commonly used clinical method of chemiluminescent immunoassay (CLIA). The developed method was versatile and could be easily extended to other proteins quantitative analysis, especially for specific biomarker determination.
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