Amperometric detection of enzymes in capillary zone electrophoresis based on dynamic modification with surfactants

Malic dehydrogenase (MD), glucose oxidase (GOD) and amino acid oxidase (AAD) are chosen as examples of enzymes for the study of electrochemical detection (ECD) in negative polarity capillary zone electrophoresis (CZE). The addition of 0.5 mM cetyltrimethylammonium bromide (CTAB) as a modifier reduces the interaction between the biomolecules and the inner wall of the capillary. Furthermore, the Cu working electrode shows stable response in such a system and the relative standard deviation is only 5.2% for 20 consecutive injections. The proposed method could offer higher sensitivity for the determination of the enzymes. The detection limits were 0.18 amol (1.2 × 10−10 M) for MD, 7.0 amol (5.0 × 10−9 M) for GOD and 28.8 amol (2.4 × 10−8 M) for AAD, respectively.