Direct Measurement of Equilibrium Constants for Water-soluble Porphyrin with Copper(II) and Cobalt(II) by Differential Pulse Anodic Stripping Voltammetry(DPASV)
Direct Measurement of Equilibrium Constants for Water-soluble Porphyrin with Copper(II) and Cobalt(II) by Differential Pulse Anodic Stripping Voltammetry(DPASV)
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差动脉冲阳极溶出伏安法(DPASV)直接测定水溶性卟啉与铜(II)和钴(II)的平衡常数
DOI：
10.1142/s1088424612004550
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发表时间：
2012
影响因子：
1.5
通讯作者：
Md. Kutubi and Masaaki Tabata
中科院分区：
文献类型：
--
作者：
Nanda Gunawardhana;Shingo Homi;Masaaki Tabata;Md. Kutubi and Masaaki Tabata
由于卟啉稳定常数高，金属化反应速度慢，准确测定金属卟啉的稳定常数比较困难。本文提出了一种使用金工作电极通过差示脉冲阳极溶出伏安法（DPASV）测定铜（II）或钴（II）与2，3，7，8，12，13，17，18-八溴-5，10，15，20-四（N-甲基吡啶-4-基）卟啉H2（OBTMPyP（4））4+的稳定常数的新方法。在旋转圆盘金电极、金属沉积、金属溶出、电位脉冲幅度和脉冲宽度的最佳条件下，在H_2（OBTMPyP（4））_4 ~+为10 ~（-7）~ 10 ~（-8）M的平衡条件下，直接测定了低至10 ~（-7）~ 10 ~（-8）M的游离Cu（Ⅱ）或Co（Ⅱ）离子的浓度。此外，支持电解质的影响，达到化学平衡的时间和测定方法（标准加入和校准曲线法）的总游离金属离子被认为是。四甲基氯化铵，（CH 3）4 N +Cl-（TMAC），显示出在其他电解质如Na 2SO 4，NaNO 3，NaCl中金属的最低检测限：在I = 0.1（（CH 3）4 N +Cl-）时，Cu（II）为0.5 ppb。在I = 0.1（CH 3）4 N +Cl-）和25 °C时，Cu（II）和Co（II）的稳定常数K_s分别为1013.93和109.47M ~（-1），K_s定义为M ~（2+）+P ~（2-）= MP（M = Cu（II）和Co（II），H ~ 2 P = H ~ 2（OBTMPyP（4））4+）。工作电极也在较高的电位下被电化学活化，从而提供较低的金属离子检测限以及测量低至10- 5 M的金属离子、卟啉和金属卟啉的循环伏安法。Cu ~（2+）、H_2（OBTMPyP（4））~（4+）和Cu（OBTMPyP（4））~（4+）的Eap（vs.Ag/AgCl）分别为345、338和425。
Because of high stability constants and slow metalation rate of porphyrins, it is difficult to determine stability constants of metalloporphyrins correctly. We propose here a new method for the determination of the stability constant of Cu(II) or Co(II) with 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin, H2(OBTMPyP(4))4+, by differential pulse anodic stripping voltammetry (DPASV) using a gold working electrode. The concentrations of free Cu(II) or Co(II) ion as low as 10-7–10-8M were determined directly in equilibrium with H2(OBTMPyP(4))4+of 10-7–10-8M under optimum DPSAV conditions of rotating disk gold electrode, deposition of metals, stripping of metals, potential pulse amplitude and pulse width. Furthermore effects of supporting electrolytes, time for the attainment of chemical equilibrium and determination methods (standard addition and calibration curve methods) of total free metal ions were considered. Tetramethylammonium chloride, (CH3)4N+Cl-(TMAC), showed the lowest detection limit of metals among other electrolytes such as Na2SO4, NaNO3, NaCl: 0.5 ppb for Cu(II) at I = 0.1((CH3)4N+Cl-). The stability constants of Ksdefined as M2++ P2-= MP (M = Cu(II) and Co(II), and H2P = H2(OBTMPyP(4))4+) were 1013.93and 109.47M-1for Cu(II) and Co(II), respectively, at I = 0.1(CH3)4N+Cl-) and 25 °C. The working electrode was also electrochemically activated at higher potential affording to lower detection limit of metal ions as well as to measure cyclic voltammetry of metal ions, porphyrin and metalloporphyrin as low as 10-5M. The values of Eap(vs.Ag/AgCl) of Cu2+, H2(OBTMPyP(4))4+and Cu(OBTMPyP(4))4+were 345, 338 and 425, respectively.