Why robust background electrolytes containing multivalent ionic species can fail in capillary zone electrophoresis

In this paper it is demonstrated that system peaks are induced by multivale nt weak ionic species in background electrolytes. Their existence is derive d from SystCharts and from Peak Shape Diagrams and the theory is confirmed experimentally. If analytes are present in a sample, with mobilities approx imately equal to the mobility of a system peak, they interact, resulting in a strong increase of electromigration dispersion. This leads to strong pea k broadening, peak deformation and a loss of resolution. Typical background electrolytes containing multivalent ionic species, e.g. phosphate and phth alate buffers, often reported to be robust electrolytes, an therefore not a lways universally applicable and can fail for the application of specific a nalytes. This paper reports a systematic study of the above phenomena and s hows both theoretical and experimental results for background electrolytes containing phosphoric acid and phthalic acid. (C) 2001 Elsevier Science B.V . All rights reserved.