Analysis of basic pharmaceuticals by capillary electrophoresis in coated capillaries and on-line mass spectrometric detection

Basic pharmaceuticals were separated using capillary electrophoresis (CE) and positively identified with the aid of an on-line coupled sectorfield mass spectrometer (MS). The coupling device consisted of a modified electrospray (ES) ion source with coaxial sheath liquid. The adaptation of the CE-conditions for the particular needs of ES-MS is discussed in brief. Applying volatile buffers of low ionic strength and using uncoated capillaries in CE causes limited sample loadability, poor peak shapes and decreases resolution. The separation performance can be significantly improved if the capillaries are coated with poly(ethylene glycol) (PEG) or poly(vinyl alcohol) (PVA). As extracted from the reconstructed ion current of the mass spectra, the baseline separated signals of structurally very similar compounds can be achieved. Signals due to the protonated and Na+-attached molecules have been observed. Nozzle-skimmer dissociation may be a versatile tool for additional molecular structure information.