Alignment of laser-induced fluorescence and mass spectrometric detection traces using electrophoretic mobility scaling in CE-LIF-MS of labeled N-glycans

The combination of optical detection techniques like photometry (UV) or laser-induced fluorescence (LIF) with mass spectrometry for capillary electrophoresis offers advantages, both for later use of stand-alone CE-UV or CE-LIF systems and for combined CE-UV-MS or CE-LIF-MS analysis. Faster method development is enabled, the identification of analytes is facilitated, and it allows christian the optical detection scheme to be used for more precise quantification. However, shortcomings of current methodology and equipment hindered the broader use of such detection combinations mainly due to the long distance between the detection points (at least 20 cm). Large shifts in migration times and changes in resolution are visible between the detection traces hindering their straightforward comparison. We present here novel equipment for a robust coupling of CE-LIF-MS with the shortest possible distance between detection points (12 cm) determined by the length of the electrospray needle. In addition, we encourage the use of a normalization of detection traces using a scale of effective electrophoretic mobility to obtain the same x-scale for both detection traces. As an example, the proposed methodology is applied to a mixture of labeled as well as non-labeled N-glycans.