Advantages of pressurization in capillary electrophoresis/electrospray ionization mass spectrometry

In this paper we present a simple interface for coupling capillary electrophoresis (CE) to mass spectrometry (MS) which can operate without significant user intervention. The use of a dedicated interface allows rapid changeover between CE/MS and liquid chromatography (LC)/MS, which is particularly important as CE and LC are often used on the same mass spectrometer, The suitability of the interface construction is illustrated on a triple quadrupole mass spectrometer and a high-resolution time-of-flight mass spectrometer with compounds such as peptides, vitamins, and carbohydrates. Separations of these compounds are also used to evaluate the robustness of the CE-MS interface under pressurized and nonpressurized modes of operation. The simultaneous application of pressure and voltage overcomes two of the major problems commonly encountered when coupling CE to MS, i.e. unreliable long-term operation and protracted analysis times due to the long separation capillaries needed to connect to the mass spectrometer, Concomitant application of high voltage and hydrostatic pressure significantly reduces analysis time without compromising the overall separation. It was observed that pressurized CE exhibits less run-to-nm-variations, leading to run-to-run repeatability better than 0.5% for migration time and below 5% for peak area with the MS as detector.