Gold-nanoparticle extraction and reversed-electrode-polarity stacking mode combined to enhance capillary electrophoresis sensitivity for conjugated nucleosides and oligonucleotides containing thioether linkers.

We present a capillary electrophoresis method for determining two different C8-conjugated deoxyadenosines, and for oligonucleotides containing them, in which a psoralen or an acridine molecule is bonded to the base via a short alkyl chain containing sulfur ethers at both ends. The sensitivity of the micellar electrokinetic chromatography (MEKC) method was increased by using two preconcentration techniques, micro solid-phase extraction (μSPE) followed by reversed-electrode-polarity stacking mode (REPSM). Variables that affect the efficiency of the extraction in μSPE and preconcentration by REPSM, including the type and volume of extraction nanoparticle, concentration, and injection time, were investigated. Under the optimum conditions, enrichment factors obtained were in the range 360-400. The limits of detection (LODs) at a signal-to-noise ratio of 3 ranged from 2 to 5 nmol L(-1). The relative recoveries of labelled adenosines from water samples were 95-103%. The proposed method provided high enrichment factors and good precision and accuracy with a short analysis time. On the basis of the advantages of simplicity, high selectivity, high sensitivity, and good reproducibility, the proposed method may have great potential for biochemical applications.