State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China.
Tianjin Key Laboratory of Environmental Technology for Complex Trans-Media Pollution, College of Environmental Science and Engineering, Nankai University, Tianjin 300050, China.
Environ Sci Technol. 2024 Aug 13;58(32):14575-14584. doi: 10.1021/acs.est.4c04520. Epub 2024 Aug 2.
The chromogenic reaction between 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and ferrate [Fe(VI)] has long been utilized for Fe(VI) content measurement. However, the presence of electron-rich organic compounds has been found to significantly impact Fe(VI) detection using the ABTS method, leading to relative errors ranging from ∼88 to 100%. Reducing substances consumed ABTS and resulted in underestimated Fe(VI) levels. Moreover, the oxidation of electron-rich organics containing hydroxyl groups by Fe(VI) could generate a phenoxyl radical (Ph), promoting the transformation of Fe(VI) → Fe(V) → Fe(IV). The in situ formation of Fe(IV) can then contribute to ABTS oxidation, altering the ABTS:Fe(VI) stoichiometry from 1:1 to 2:1. To overcome these challenges, we introduced Mn(II) as an activator and 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic agent for Fe(VI) detection. This Mn(II)/TMB method enables rapid completion of the chromogenic reaction within 2 s, with a low detection limit of approximately 4 nM and a wide detection range (0.01-10 μM). Importantly, the Mn(II)/TMB method exhibits superior resistance to reductive interference and effectively eliminates the impact of phenoxyl-radical-mediated intermediate valence iron transfer processes associated with electron-rich organic compounds. Furthermore, this method is resilient to particle interference and demonstrates practical applicability in authentic waters.
ABTS 与高铁酸盐之间的显色反应长期以来一直被用于高铁酸盐含量的测量。然而，已经发现富电子有机化合物的存在会显著影响 ABTS 法检测高铁酸盐，导致相对误差范围在 88%到 100%之间。还原物质消耗 ABTS，导致高铁酸盐水平被低估。此外，高铁酸盐可以氧化含有羟基的富电子有机物，生成苯氧自由基（Ph），促进高铁酸盐向 Fe(V)→Fe(IV)的转化。Fe(IV)的原位形成可以促进 ABTS 的氧化，从而改变 ABTS:Fe(VI)的化学计量比从 1:1 变为 2:1。为了克服这些挑战，我们引入 Mn(II)作为激活剂和 3,3',5,5'-四甲基联苯胺（TMB）作为显色剂来检测 Fe(VI)。这种 Mn(II)/TMB 方法能够在 2 秒内完成显色反应，检测限约为 4 nM，检测范围较宽（0.01-10 μM）。重要的是，Mn(II)/TMB 方法对还原干扰具有优异的抗性，并有效地消除了与富电子有机化合物相关的苯氧自由基介导的中间价态铁转移过程的影响。此外，该方法对颗粒干扰具有较强的抵抗力，在实际水样中具有实际应用价值。
