Programmed Nebulizing Gas Pressure for Efficient and Stable Capillary Electrophoresis−Mass Spectrometry Analysis of Anionic Compounds in Positive Separation Mode

Here we have developed a method for the analysis of anionic compounds by capillary electrophoresis coupled to electrospray ionization-mass spectrometry (CE-ESI-MS). The strategy proposed is based on the application of programmed nebulizing gas pressure (PNP), which is applied during the different steps of analysis: sample injection, electrophoretic separation, and detection by the mass spectrometer. The proposed procedure prevents the frequent drops in current observed in the analysis of anions and allows high separation efficiency by capillary electrophoresis to be maintained because it is not necessary to employ pressured-assisted electrophoresis. Additionally, for the first time we describe the use of 100 μm capillaries in capillary electrophoresis-mass spectrometry, allowing the loading of larger samples and hence greater sensitivity, with no loss of the efficiency achieved with the 50 μm capillaries usually used.