MARKER TECHNIQUES FOR HIGH-ACCURACY IDENTIFICATION IN CZE

Marker techniques have been developed for high-accuracy identification by capillary zone electrophoresis. The techniques employ two, three, or four markers of known electrophoretic mobilities which are used to determine the effective electric field strength (E(eff)) and electroosmotic now velocity (upsilon(eo)) of a system, E(eff) was always approximated to stay constant within one ran. With different numbers of markers, different assumptions were made about the time dependence of upsilon(eo) within one run. With two markers, upsilon(eo) was approximated to stay constant, whereas with three or four markers it was approximated to be linearly and nonlinearly accelerating, respectively. The information about E(eff) and upsilon(eo) together with the electrophoretic mobilities of the marker compounds, was used to determine the electrophoretic mobilities of unknown compounds. Extremely high repeatabilities (0.01-0.03%) were obtained for compounds with pK(a) values far from the pH of the electrolyte solution. Because electrode reactions alter the pH of the electrolyte solution, however, systematic drift in the mobility was found for one compound with a pK(a) value close to the pH of the electrolyte. In such situations, where analytes may have pK(a) values close to the pH of the electrolyte, fresh electrolyte should be supplied for every run. The reliability of the identification-was increased up to 350-fold relative to the use of absolute migration times.