Wen-Bao Chang

Sulfonamide imprinted polymers using co-functional monomers

Abstract Molecular imprinted polymers (MIPs) prepared using combination of acrylamide (ACM) and 4-vinylpyridine (4-Vpy) as co-functional monomers exhibited efficient recognition properties in both organic and aqueous media as HPLC stationary phase. The results indicate that amide and pyridine groups in functional monomers formed strong hydrogen-bonding interaction with the template molecule, and specific recognition sites were created within the polymer matrix during the imprinting process. When sulfamethoxazole (SMO) was used as template, a MIP prepared in a polar organic solvent (acetonitrile) using the combination of ACM and 4-Vpy showed better recognition of template than the polymer prepared in the same solvent using the combination of acidic monomer (methacrylic acid) and basic monomer 4-Vpy. On the contrary, when sulfamethazine (SMZ) was used as template, a MIP prepared using the combination of methacrylic acid (MAA) and 4-Vpy showed better recognition of template than the polymer prepared using the combination of ACM and 4-Vpy. Our results indicate that in organic media the degree of retention of the sample molecules on the imprinted polymers was controlled by the hydrogen-bonding interaction between the sample molecules and the polymer, while in aqueous media it was determined to a considerable extent by hydrophobic interactions. In both media the shape, size and the electronic structure of the template molecule were all-important factors in the recognition process.

Kinetic deoxyribose degradation assay and its application in assessing the antioxidant activities of phenolic compounds in a Fenton-type reaction system

Abstract Pro-oxidant properties of phenolic antioxidants, which are derived from their iron recycling reactivity, render the traditional deoxyribose degradation assay invalid to assess the hydroxyl radical-scavenging activity in Fenton-type reaction systems. In the present paper, we studied in detail the interactions between iron and phenolic compounds, and established a kinetic deoxyribose method by taking advantage of the distinct difference between the completion time of Fenton reaction and that of the iron-reducing process. With the newly established kinetic method, we investigated the effects of phenolics on hydroxyl radical formation in a Fenton-type system and determined successfully the second rate constants of hydroxyl radical-scavenging reactions. The site-specific and non-site-specific hydroxyl radical-scavenging ability suggested that both direct hydroxyl radical-scavenging potency and iron-chelating capacity accounted for their inhibitory effects on deoxyribose oxidation degradation. This method, more simple, time saving, and applicative than the traditional deoxyribose assay, produces as accurate results (RSD

Electrocatalytic reduction of dioxygen on hemin based carbon paste electrode

A hemin-modified carbon paste electrode was constructed by a simple, rapid and effective method. The electrochemical behaviour of the modified electrode was characterized by cyclic voltammetry. The modified electrode obtained was very stable and exhibited electrocatalytic response for the reduction of oxygen. The possible mechanism for the catalytic reduction of dioxygen is discussed. The dioxygen is reduced via a one-step reduction accompanying four electrons and four protons transfer at pH 7–11.

Chromatographic characterization of sulfonamide imprinted polymers

Sulfamethazine and sulfamethoxazole are anti-bacterial and anti-infective agents. Molecular imprinted polymers of these agents were prepared by the technique of non-covalent molecular imprinting polymerization. The functional monomers used include methacrylic acid, 4-vinylpyridine, acrylamide or a combination of methacrylic acid and 4-vinylpyridine. The polymers obtained were packed in a high-performance liquid chromatography (HPLC) column, and the molecular recognition mechanism regulating the binding behavior was studied using chromatography. The results showed that methacrylic acid was suitable for synthesizing sulfamethazine-selective polymer, whereas 4-vinylpyridine was suitable for sulfamethoxazole. Although these two compounds have similar structures, the interactions between them and the monomers are different. The selective polymers are expected to be of use for analyzing sulfonamide compounds in the food industry and clinic applications.

Comparative study on heme-containing enzyme-like catalytic activities of water-soluble metalloporphyrins

Abstract This paper reported the heme-containing enzyme-like catalytic activities of 15 water-soluble metalloporphyrins (M-Ps) produced from three metal ions (Fe, Mn and Co) and five porphophine ligands, i.e. porphyrin IX, meso-tetrakis(p-sulfonatophenyl)porphophine (TPPS4), meso-tetrakis(4-carboxy-phenyl)porphophine (TCPP), meso-tetrakis[4-(N-trimethyl)aminophenyl]porphophine (TTMAPP) and meso-tetrakis(4-N-methylpyridinium)porphophine (TMPyP). Their catalytic activities of catalase, peroxidase and cytochrome P-450 on the typical reactions were systematically studied and compared. The results indicated that the metalloporphyrins with Fe and Mn as central ions show high catalytic activities of catalase and peroxidase at pH range of 10.5–11.5, and among them Fe-TMPyP and Fe-TTMAPP have the highest catalytic capability, while all Co-porphyrins have weak activities. Interestingly, only Mn-TMPyP of the 15 metalloporphyrins shows relatively high cytochrome P-450-like activity. The presence of imidazole has enhancement effects to different extent on the peroxidase-like activities of these metalloporphyrins and negligible effects on catalase-like activities.

Determination of Morphine by Capillary Zone Electrophoresis Immunoassay Combined with Laser‐Induced Fluorescence Detection

Abstract A competitive immunoassay for detecting morphine in bio‐samples was established by capillary zone electrophoresis combined with laser‐induced fluorescence detection (CZE‐LIF). The antigen of morphine was labeled with isothiocyano‐fluorescein (FITC) and then incubated with morphine monoclonal antibody and samples. The linear range was 50–1000 ng/mL, which was suitable for clinical and forensic applications. The detection limit can reach 40 ng/mL, based on S/N = 2. The recoveries of morphine from serum were satisfactory.

RETRACTED: Quantitative elucidation of the molecular mechanisms of hydroxyl radical quenching reactivity of phenolic compounds

Reported discrepancies have confused the understanding of the molecular mechanisms of antioxidant reactivity somewhat. The consequent problems necessitate systematic investigations on the molecular orbital features of antioxidants and their correlation with antioxidant potentials. In the present work, phenolic compounds as typical antioxidants were selected to investigate their hydroxyl radical-scavenging properties, and the related mechanisms of action were studied theoretically by computational chemistry. A good correlation was observed between antioxidant activity and theoretical parameters, such as O-H bond dissociation energy (BDE), ionization potential (IP), enthalpy of electron transfer (E(a)), chemical hardness (HOMO-LUMO gap), and spin delocalization of the phenoxyl radicals (D(s)(r)). The results demonstrate that the molecular mechanisms regulating the antioxidant action were more complex than hydrogen or electron-transfer processes and explain previous contradictions. Meanwhile, a satisfactory quantitative structure-activity relationship (QSAR) model was established which should be of predictive value in evaluating or screening hydroxyl radical-scavenging antioxidants.

Synthesis of enantiomeric selective α1-acid glycoprotein (AGP)-bonded capillary and its application in capillary electrophoresis

Abstract α1-Acid glycoprotein (AGP) was bonded to a fused silica capillary using 3-(2,3-oxopropoxypropyl, trimethylsilane as bridging reagent. The capillary can be used for the direct enantiomeric separation of some basic pharmaceuticals in capillary zone electrophoresis. The related operation parameters such as pH, salt concentration, organic modifiers in the buffer have been studied. It is demonstrated that an AGP-bonded capillary could be used in the different buffer solutions and under operation conditions in capillary electrophoresis with good stability.

A new spectrophotometric method for the determination of aniline in environmental water samples.

ABSTRACT A new spectrophotometric method has been established to determine trace aniline in water samples. A mixture solution of N-chlorosuccinimide and 8-hydroxyquinaldine in N, N-dimethylformamide (DMF) was used to react with the aniline in water at room temperature (20°C). When the solution was adjusted to pH 10-11 by adding 3 mol/L NaOH, a clear and blue-colored dye formed immediately with the maximum absorption wavelength at 615 nm. Molar absorptivity and detection limit were found to be 1.0×104 L mol−1 cm −1 and 30 μg/L, respectively. Linearity was excellent in the concentration range of 0.2 to 15 mg/L aniline in water sample. The proposed method has been used to analyze aniline in surface and sewage water samples with the recoveries 96-103% and relative standard deviation less than 3%. Its a promising method to be applied for routine analysis of aniline in water.

Determination of Papaverine by Biotin‐Avidin Amplified ELISA

Abstract Papaverine [1‐(3,4‐dimethoxybenzyl)‐6,7‐dimethoxyisoquinoline; PAP] is one of the most important alkaloids among the naturally occurring opium alkaloids. This work developed an indirect competitive enzyme‐linked immunosorbent assay (ELISA) for PAP based on the biotin‐avidin amplification system. The linear range of the calibration curve and the limit of detection (defined as three times of the blank) were 0.02–1000 ng/mL and 0.008 ng/mL, respectively. The established method was successfully applied to determining the concentration of PAP in the pericarpium papaveris with the recoveries between 88% and 120%. It was proved to be a highly sensitive and practical method for trace PAP detection compared with the existing gas chromatography‐mass spectrometry (GC‐MS) or high‐performance liquid chromatography (HPLC) methods.