Alternatives for coupling sequential injection systems to commercial capillary electrophoresis–mass spectrometry equipment

On-line coupling of an automated flow system with a commercially available capillary electrophoresis (CE) system with an electrospray interface (ESI) for mass spectroscopic (MS) detection is described. The peculiarities of CE–ESI-MS interfaces, in which a high electrical field must be applied to the capillary end where the sample is provided by the flow system, introduce significant difficulties for the appropriate work of the entire arrangement. Experimental strategies are proposed for achieving stable conditions for on-line sample pre-treatment, conditioning of the separation capillary, sample injection, as the proper separation. The versatility and robustness of the proposed arrangement is discussed, taken as example the separation of a variety of amines. Connection of the CE system's pressure to the automated flow system enables hydrodynamic introduction of sample with high precision. The developed hyphenated system is of practical relevance as it opens an avenue for the simplification and automation of the whole analytical process required when using powerful CE–ESI-MS equipments.