AUXILIARY ELECTROOSMOTIC FLOW FOR POSTCAPILLARY REACTION DETECTION INCAPILLARY ELECTROPHORESIS

The application of a supplementary potential at the end of a separatio n capillary has been evaluated for the introduction of a reagent solut ion for postcapillary reaction detection. Analyte zones emerging from the capillary were introduced into a short (similar to 2 cm) reaction capillary that was aligned with the separation capillary. The efficien cy of transfer of the analyte zones to the reaction capillary and the relative flow of reagent solution and separation electrolyte into the reaction capillary were a function of the applied potential at the int ersection of the two capillaries. Capillaries having i.d. values of 75 , 50, and 25 mu m were investigated. When a 2 cm X 25 mu m i.d. reacti on capillary was added to a 60 cm X 25 mu m i.d. separation capillary, the change in peak dispersion for the transfer of nitrite peaks acros s the gap and through the reaction capillary was small (decrease from 420 000 to 400 000 theoretical plates) when the percent flow from the reagent reservoir was 30% of the total combined flow. The influence of displacement between the capillaries on peak transfer was similar for both axial and vertical directions over the range of 1-50 mu m. A pot ential application examined for this detection system was the addition of a 0.4 mol/L strong base solution to permit the electrochemical det ection of carbohydrates separated in a berate buffer system.