Determination of metal content in superoxide dismutase enzymes by capillary electrophoresis†

Superoxide dismutases are antioxidant scavenger enzymes that contain a metal cofactor (copper, zinc, iron, and manganese) in their active site. Metal content measurement is one of the essential steps to characterize enzyme biological activity. We have developed a capillary electrophoretic protocol for the determination of the metal content in superoxide dismutase enzymes. The background electrolyte containing 10 mM pyridine-2,6-dicarboxylic acid and 1 mM 1-methyl-3-tetradecylimidazolium chloride at pH 3.8 was optimized for on-column complexation of the above-mentioned metals. The minimum detectable levels of metals ranged from 0.3 to 1.2 μg/mL. The reliability of the method was checked by parallel quantitative determination of the metal content in superoxide dismutase enzymes by graphite furnace or flame atomic absorption spectrophotometry methods.