Novel Fluorometric Method for the Determination of Production Rate and Steady-State Concentration of Photochemically Generated Superoxide Radical in Seawater Using 3鈥?6鈥?(Diphenylphosphinyl)fluorescei

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• 作者：Adebanjo Jacob Anifowose ; Kazuhiko Takeda ; Hiroshi Sakugawa
• 刊名：Analytical Chemistry
• 出版年：2015
• 出版时间：December 15, 2015
• 年：2015
• 卷：87
• 期：24
• 页码：11998-12005
• 全文大小：407K
• ISSN：1520-6882

文摘

Superoxide radical (O₂^{鈥⑩€?/sup>) is an important reactive oxygen species in seawater. Measurements of its production rates and steady-state concentrations generated by photochemical processes have been a Herculean task over the years. In this study, a probe 鈥?3鈥?鈥?(diphenylphosphinyl)fluorescein (PF-1) 鈥?was used to trap photochemically generated O₂鈥⑩€?/sup> in seawater, thereby yielding fluorescein. The fluorescein produced was measured by an isocratic fluorescence HPLC at excitation/emission wavelengths of 490/513 nm, respectively. The reaction rate constant of PF-1 with O₂鈥⑩€?/sup> (k_PF-1) was pH-dependent: (3.2鈥?3.5) 脳 107 M鈥? s鈥? at pH_TOT 7.65鈥?.50. By applying appropriate equations, both the production rate and the steady-state concentration of O₂鈥⑩€?/sup> generated by photochemical reactions in the seawater were quantified. Under the optimized experimental conditions, fluorescein standards (3鈥?0 nM) exhibited linearity in the seawater by HPLC. The photoformation of fluorescein, due to the reaction of PF-1 with the O₂鈥⑩€?/sup> photochemically produced in the seawater, was linear within the 20 min irradiation. The detection limit of the fluorescein photoformation rate was 0.03 pM s鈥?, defined as 3蟽 of the lowest standard fluorescein concentration per 20 min irradiation. Using this value, the yield of fluorescein, and the fraction of O₂鈥⑩€?/sup> that reacted with PF-1 in the seawater, the detection limit of the O₂鈥⑩€?/sup> photoformation rate was 1.78 pM s鈥?. Superoxide measurements using the proposed method were relatively unaffected by the potential interfering species in seawater. Application of the proposed method to ten (10) seawater samples from the Seto Inland Sea, Japan, resulted in measured O₂鈥⑩€?/sup> photoformation rates of 3.1鈥?.5 nM s鈥?, with steady-state concentrations ranging (0.06鈥?.3) 脳 10鈥?0 M. The method is simple, requires no technical sample preparation, and can be used to analyze a large number of samples.}