Determination of nucleosides in serum by two-dimensional magnetic solid-phase extraction microfluidic chip/liquid chromatography-mass spectrometry

A two-dimensional magnetic solid-phase extraction microfluidic chip (2D-MSPE-chip) was designed in this paper. A microcolumn array was integrated before two serially connected extraction chambers to filter particles in the sample. The two magnetic nanomaterials with orthogonal separation mechanism of Fe₃O₄@UiO-66-C18 and Fe₃O₄@MOF@COF-B(OH)₂ were filled into the extraction chamber, respectively, and were used to effectively eliminate matrix effects and enrich the targets. The 2D-MSPE-chip was combined with liquid chromatography-mass spectrometry (LC-MS) for the determination of eight nucleosides in serum samples. The validation results showed that the 2D-MSPE-chip/LC-MS method had excellent linear range (2–1000 ng/mL), high sensitivity (detection limit of 0.02–0.22 ng/mL), good repeatability (intra-day precision ≤5.2%, inter-day precision ≤7.2%) and a negligible absolute matrix effect (93.1%-101.9%). The recovery rate of the spiked serum samples of prostate cancer patients and healthy person was 90.8%-109.1%, indicating a high accuracy. The inosine level decreased and adenosine level increased in the serum of prostate cancer patients (p < 0.01), suggesting the correlation between nucleosides and the cancer.