Quantification of Hydroxyl Radical Generated from the Fe²⁺-H₂O₂ and Cu²⁺-H₂O₂ Reaction Systems by Electron Spin Resonance Stop and Flow Technique

抄録

When quantifying hydroxyl radical (•OH) generated from the Fe²⁺-H₂O₂ or Cu²⁺-H₂O₂ reaction system, it is very important to know the real-time profile of •OH generation. In this study, we examined the real-time profile of DMPO-OH generated from •OH generation systems using the electron spin resonance (ESR) stop and flow technique. Temporal changes in the amount of •OH were observed, and several generation patterns were evident in the Fe²⁺-H₂O₂ and Cu²⁺-H₂O₂ reaction systems. From the Fe²⁺-H₂O₂ reaction system, three typical patterns of •OH generation were observed. The •OH was generated violently at first, and then decreased rapidly (destruction type) or slowly in a stable manner (destruction-plateau type); sometimes, •OH was not detected (negative type). On the other hand, two typical patterns of •OH generation were observed from the Cu²⁺-H₂O₂ reaction system. The amount of •OH generated reached a peak at an early stage and then decreased rapidly (decrease type) or reached a plateau (plateau type). These results suggest that the amount of •OH generated changes depending upon the concentration of the metal ion and H₂O₂ in both the Fe²⁺ and Cu²⁺-H₂O₂ reaction systems.