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 m id column filled with particles of 90 m followed by a separation capillary with 50 m 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 L of sample. This corresponds to an enrichment factor of more than 800 compared to the corresponding CE-MS method without preconcentration.