The original pyrogallol (1,2,3-trihydroxybenzene) method, which was developed specifically for superoxide dismutase, is now widely used for measuring superoxide-scavenging of other antioxidants. However, the strong pH effect has been ignored. In this study, the influencing factors have been systematically investigated for the first time, and a number of experiments have proved that the pH is of major importance. As major antioxidants contain carboxylic acid, ester, or lactone groups, pH 8.2 should be modified to physiological pH 7.4. The improved procedure is as follows. A pyrogallol solution (in 1 M HCl) is thoroughly mixed with pH 7.4 Tris-HCl buffer; A325 nm is measured every 30 s for 5 min at 37 °C. As the ΔA325 nm, control value reflects the initial concentration of substrate •O2–, it should be well controlled to guarantee the accuracy of the method. The improved pyrogallol method is a reliable and cheap superoxide-scavenging assay suitable for all types of antioxidants.
Lin Zhou,Xuan Chen,Zhanghong Guo,Haining Cui,Jinxin Ma,Qijun Song
Metal nanoclusters (MNCs) have attracted widespread attention due to their unique subnanometer size, tunable fluorescence emission, and excellent biocompatibility. However, the enzyme-like activity and the optical properties of MNCs are rarely exploited simultaneously. Here, iridium nanoclusters (Py-IrNCs) with excellent fluorescence properties and the laccase-like activity were synthesized by the reduction of IrCl 3 with NaBH 4 in the presence of pyrogallol. The laccase activity of Py-IrNCs exhibited in the catalytic transformation of 2,4-dichlorophenol (2, 4-DP) is substantially superior to that of natural laccase, which is manifested by the fact that the amount of Py-IrNCs was only 2.5% of natural laccase to achieve the same catalytic performance. In the coexisting of 4-aminoantipyrine (4-AP), a distinct color change and quench of fluorescence were observed; thus, a sensitive colorimetric and fluorescence dual-mode determination of 2,4-DP was achieved with a linear range of 0–40 μM and a limit of detection of 0.5 μM. The dual-mode detections can be mutually verified, which effectively improved the reliability of the analysis, demonstrating a promising application potential of Py-IrNCs in pollutant determination.
Jinsong He,Yan Wang,Fan Ni,Fei Shen,Shihuai Deng,Yanzong Zhang,Lulu Long,Ling Luo,Yan Liu
Loose nanofiltration membrane (LNM) with high separation toward dye/salt and high permeability is a promising candidate for resource recovery of textile wastewater. In this study, to prepare a high permeable LNM, a ternary coating system containing a small polyphenol molecule named pyrogallol (PG), polyethylenimine (PEI) and Fe 3+ ion was co-deposited on the hydrolyzed polyacrylonitrile substrate via regulating the competition reactions between coordination bond (COB) and covalent bond (CB). The membrane formation mechanism, morphology, surface properties, and separation performance of dye/salts were investigated by characterizations and filtration experiments. The characterization results indicated that the addition of Fe 3+ limited the CB formation between PG and PEI via Michael addition and Schiff base reaction, due to its strong coordination ability toward PG and PEI via COB with –OH and –NH- groups, further reducing the selective layer thickness and improving the membrane permeance as a result. The content of PEI and Fe 3+ in ternary coating solution obviously affected membrane morphology and hydrophilicity, thus influencing the permeance. More importantly, The LNM-5 exhibited an ultrahigh water permeability of 141.5 LHM·bar −1 , high rejection of Congo Red (CR, 99.5%) and Alcian blue 8GX (ALBL, 99.7%) as well as high transmission of salts (98.8% for NaCl, 97.3% for Na 2 SO 4 , respectively.), which performed much better than many reported state-of-the-art LNMs prepared by different methods. Even under 60 g/L salt content, high rejection of CR (99.1%) and high pass of salts (98.8% for Na 2 SO 4 ) could be still maintained. Furthermore, the LNM-5 had a superior antifouling performance and long-term stability during filtration (22 h) of dye/salt mixture. This work indicated that small polyphenol/PEI/Fe 3+ trinity coating could be used as a promising alternative in practical applications, realizing excellent molecular separation towards sustainable textile wastewater remediation.
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