The simultaneous determination of cationic, anionic, and neutral analytes in a real sample was demonstrated by coupling electrochemical (EC) derivatization with counter-EOF CE-(CD)-D-4. An EC flow cell was used to oxidize alcohols from an antiseptic mouthwash sample into carboxylic acids at a platinum electrode in acid medium. The carboxylates formed in the derivatization process and other sample ingredients, such as benzoate, saccharinate, and sodium ions, were separated in counter-flow mode and detected in one run in Tris-HCl buffer, pH 8.6. Fewer than 5 min were needed to complete each analysis with the automated flow system comprising solenoid pumps for the management of solutions. Insights into the electrochemistry of benzoic acid, present in the sample matrix, were also gained by EC-CE-(CD)-D-4; more specifically, by applying potentials higher than 1.47 V to the platinum electrode, some formiate and minute amounts of salicylate were detected.