Robust and cost-effective capillary electrophoresis-mass spectrometry interfaces suitable for combination with on-line analyte preconcentration

This paper describes several successful cost-effective attempts to couple c apillary electrophoresis (CE) and mass spectrometry (MS) without make-up fl ow or nebulizing gas. An in-depth analysis of several interfaces using cond uctive spray tips was performed as well as an easy-to-prepare T-junction wi th direct electrode contact, the latter being the most robust interface. No coating is necessary and the spray voltage is applied through a gold wire positioned at the gap between the separation and spray capillaries. The T-j unction interface is made by puncturing a small piece of transparent rubber . The on-line preconcentration CE-MS system allows immunoassay sensitivity, as is demonstrated by a calibration plot in the picomolar range for angiot ensin II and gonadorelin. It also shows good reproducibility and has the ab ility of excellent automation. The secure electrical contact gives a consta nt spray quality, even with 100% aqueous separation buffers. The described setup has a wide applicability as is demonstrated by the analysis of larger peptides, such as insulin and cytochrome c. Detailed information is given on critical factors in the preparation of the described interfaces.