A SIMPLE MEANS OF GENERATING PH GRADIENTS IN CAPILLARY-ZONE-ELECTROPHORESIS

Injection of a ''pulse'' of a secondary pH buffer just prior to the in jection of analyte provides a mild pH gradient within the primary pH b uffer. Separations of weakly acid or basic analytes are easily optimiz ed using this gradient. A model explaining the impact of the pulse of secondary buffer is proposed. Experiments verify that the strength of the pH gradient depends on the effective width of the pulse, the diffe rence in mobility of the analyte in the two buffers and on the differe nce in mobility between the analyte and the pulse of secondary buffer. Sixteen chlorinated phenols are baseline separated in 25 min using a 45-mM phosphate-15 mM tetraborate buffer (adjusted to pH 7.0) when 2.6 % of the capillary is filled with 22.5 mM phosphate-7.5 mM tetraborate (adjusted to pH 10.0). (C) 1997 Elsevier Science B.V.