Pseudo-electrochromatography--negative-ion electrospray mass spectrometry of aromatic glucuronides and food colours.

Pseudo-electrochromatography is a combination of liquid chromatography and an electromigration technique, especially directed at the separation of ionic compounds prior to mass spectrometric detection with a mobile phase composition compatible with mass spectrometry. The application of pseudo-electrochromatography to the separation of food colours and aromatic glucuronides is described. An example of selectivity tuning by applying voltages of differing polarity during the chromatographic run is given. The coupling of pseudo-electrochromatography with electrospray mass spectrometry is demonstrated. Differences in the effects of the axial potential over the column between silica-based and polymeric packing materials are discussed.