STUDY OF THE ELECTRODE PROCESS OF HEMOGLOBIN AT A POLYMERIZED AZURE A FILM ELECTRODE

The electrochemically polymerized azure A film electrode is reported. The resulting film on a platinum electrode surface was analyzed with electron spectroscopy for chemical analysis (ESCA). The heterogeneous electron transfer processes of hemoglobin at the polymerized azure A film electrode have been investigated using in situ UV-visible spectroelectrochemistry. The formal potential (E-degrees') and electron transfer number (n) of hemoglobin were calculated as E = 0.088 V versus NHE (standard deviation +/- 0.5, N = 4) and n = 1.8 (standard deviation +/- 0.5, N = 4). Exhaustive reduction and oxidation electrolysis are achieved in 80 and 380 seconds, respectively, during a potential step between -0.3 and +0.3 V. A formal heterogeneous electron-transfer rate constant (k(sh)) of 3.54(+/- 0.12) X 10(-6) cm/s and a transfer coefficient (alpha) of 0.28(+/- 0.01) were obtained by cyclic voltabsorptometry, which indicated that the poly-azure A film electrode is able to catalyze the direct reduction and oxidation of hemoglobin.

CATALYTIC REDUCTION OF HEMOGLOBIN AT THIONINE CHEMICALLY MODIFIED ELECTRODE AND FIA APPLICATIONS

Thionine-containing chemically modified electrode (cme) was constructed with glassy carbon substrate by potential sweep oxidation, electrodeposition and adsorption procedures, and electrocatalytic reduction of hemoglobin was carried out and characterized at the cme under batch and flow conditions. Comparison of the catalytic response toward hemoglobir obtained at the cme was made mainly in terms of the potential dependence, the detectability and long-term stability. When used in flow injection analysis (FIA) experiments with the detector monitored at a constant potential applied at -0.35 V vs sce, detection limit of 0.15-1.5 pmol level of hemoglobin injected was achieved at the cme, with linear response range over 2 orders of magnitude. All the cme s retained more than 70% of their initial hemoglobin response level over 8 h of continuous service in the flow-through system.

FLOW-INJECTION ANALYSIS OF MYOGLOBIN AND HEMOGLOBIN AT TOLUIDINE BLUE CHEMICALLY MODIFIED ELECTRODE

Electrodeposition of the phenothiazine mediator titrant toluidine blue onto a glassy carbon substrate at an appropriate potential was used to construct a toluidine blue chemically modified electrode (CME) exhibiting electrocatalytic reduction for myoglobin and hemoglobin. The CME catalyzed the hemoprotein electroreduction at the reduction potential of the mediator molecule. When the CME as used as a detector for flow injection analysis at a constant applied potential of -0.30 V vs. a saturated calomel electrode, it gave detection limits of 20 and 50 ng (1.2 and 0.78 pmol) injected myoglobin and hemoglobin, respectively, with a dynamic linear concentration range over 2 orders of magnitude. After a brief equilibration period, the CME retained nearly 90% of its initial myoglobin response over 8 hours of continuous exposure to the flow-through system.

Photocatalytic degradation of CI Acid Blue 80 in aqueous suspensions of titanium dioxide under sunlight

The dye C.I. Acid Blue 80 (AB80) was easily degraded by TiO2-P25 assisted photocatalysis in aqueous dispersion under irradiation of sunlight. The optimal reaction conditions were [TiO2] = 2.0 g/L, pH = 10, [H2O2] = 5 mmol/L. The photocatalytic reaction followed pseudo-first order kinetics. The adsorption of AB80 onto TiO2 was in accord with Langmuir equation.

Degradation of porphyran from Porphyra haitanensis and the antioxidant activities of the degraded porphyrans with different molecular weight

In the present paper, ascorbate and hydrogen peroxide (H2O2) were used to degrade porphyran. It was found that porphyran could be degraded by free radical that was generated by ascorbate and H2O2 in combination. It was possible to prepare desired porphyran products with different molecular weight by adjusting ascorbate to H,02 proportions and their concentrations. The molar ratio of I was demonstrated more effective than in other ratios. Higher concentrations accelerated the degradation. Moreover, results of chemical analysis and FT-IR spectra suggested that the main structure of degraded products still remained although some changes happened. The degraded and natural porphyrans possessed scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH)-radical activity and reducing power. Higher antioxidant activities were found in both systems when the molecular weight was reduced. The results indicated that the antioxidant activities were closely related to the molecular weight. The degraded porphyrans are potential antioxidant in vitro. (c) 2006 Elsevier B.V. All rights reserved.