Capillary electrophoresis-laser induced fluorescence-electrospray ionization-mass spectrometry: a case study

The simultaneous hyphenation of capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection and electrospray ionization-mass spectrometry (ESI-MS) as a novel combined detection system for CE is presented. beta-Carbolines were chosen as model analytes with a forensic background. Nonaqueous CE as well as conventional CE with an aqueous buffer system are compared concerning efficiency and obtainable detection limits. The distance between the optical detection window and the sprayer tip was minimized by placing the optical cell directly in front of the electrospray interface. Similar separation efficiencies for both detection modes could thus be obtained. No significant peak-broadening induced by the MS interface was observed. The high fluorescence quantum yield and the high proton affinity of the model analytes investigated resulted in limits of detection in the fg (nmol/L) range for both detection methods. The analysis of confiscated ayahuasca samples and ethanolic plant extracts revealed complementary selectivities for LIF and MS detection. Thus, it is possible to improve peak identification of the solutes investigated by the use of these two detection principles.