IMPROVED SENSITIVITY BY ONLINE ISOTACHOPHORETIC PRECONCENTRATION IN THE CAPILLARY ZONE ELECTROPHORETIC DETERMINATION OF PEPTIDE-LIKE SOLUTES

Isotachophoresis (ITP) was studied as an on-line preconcentration technique in combination with capillary zone electrophoresis for the determination of positively charged peptide-like solutes. This paper shows the effects of different electrolyte compositions, different ITP times and various injection volumes on the time necessary for stacking and destacking. Injection volumes as large as 1.4 mu 1 resulted in a resolution between the test peptides similar to that of pure capillary zone electrophoresis. Calibration graphs were linear in a range from 15 mu mol/l down to 30 nmol/l after injections of 1.4 mu l. Initial studies of plasma extracts appeared promising, although in the long term the overall efficiency decreased.