Despite many advantages like high separation efficiency CE comprises the main limitation of low concentration sensitivity, when compared to HPLC. In-line SPE is an efficient way to increase concentration sensitivity. Here, a fritless in-line-SPE-CE-MS method was developed in order to analyze anions of strong acids. Mixed-mode (weak anion exchange and RP) particles were used for enrichment and an acidic BGE was applied for separation. Different particle and capillary sizes were tested. A novel bead string design with a 100 μm id column filled with particles of 90 μm followed by a separation capillary with 50 μm id was easy to prepare and showed the best performance with respect to separation efficiency and reproducibility. Three aromatic sulfonic acids were employed in an in-line SPE-CE-UV approach for method development. Method validation was performed with respect to reproducibility, robustness, and linearity. Thereafter the method was transferred to SPE-CE-MS and applied to the analysis of glycans labeled with 8-aminopyrene-1,3,6-trisulfonic acid. Lower limits of detection in the low nM range were achieved injecting about 10 μL of sample. This corresponds to an enrichment factor of more than 800 compared to the corresponding CE-MS method without preconcentration.
Keywords: CE-MS; Glycans; Inline SPE-CE; Organic sulfonates.
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