[Show abstract][Hide abstract] ABSTRACT: Natural photosensitizer has been reported to play an important role in the sunlight-mediated degradation of organic pollutants and the self-purification of natural waters. Riboflavin (RF), a model natural photosensitizer, is widely present in-vivo and natural environments. RF has been proposed to generate reactive oxygen species (ROS) for degradation of pollutants, but it is susceptible to photodegradation because of instability of its ribose chain. In this work, the sunlight-mediated degradation of methyl orange (MO), as a model pollutant, was assessed at different pHs and initial RF concentrations. The MO photodegradation was found to be sensitized mainly by the photoproducts of RF, rather than RF itself. The highest MO photodegradation efficiency was achieved at pH 11.0. In order to further reveal its functional mechanisms, experiments were carried out in the presence of singlet oxygen (1O2) quencher (1,4-diazabicyclo[2.2.2]octane) and superoxide anion radical (O2−) quencher (1,4-benzoquinone). Only 1,4-benzoquinone was able to inhibit the photodegradation, suggesting that the photooxidation of MO was mainly initiated by O2−. The generation of O2− was further validated by electron paramagnetic resonance (EPR) spectroscopy combined with spin trapping. Possible pathways were proposed for the RF-sensitized photodegradation of MO under solar irradiation.
Separation and Purification Technology 03/2015; 142. · 3.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, the rationale for exploring the thermal deterioration mechanism of the bio-oil pyrolyzed from rice husk is established. This is based on identification of the unstable intermediates in the thermal deterioration process. Fourier transform infrared (FTIR) spectroscopy was used to monitor such a thermal deterioration process of bio-oil samples in thermal treatment and/or during long-term storage at ambient temperatures of 20-30 °C. Terminal olefins, as a key intermediate, so-called "signature", were identified qualitatively by using FTIR spectroscopy. A band shift observed at 880 cm(-1), which was assigned to the C-H out-of-plane deformation vibration of terminal olefins, indicates the start-up of the bio-oil thermal deterioration. A two-step pathway was proposed to describe the thermal deterioration process of bio-oil. This study suggests that the status of bio-oil could be rapidly monitored by the FTIR method.
Journal of Agricultural and Food Chemistry 08/2011; 59(17):9243-9. · 3.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this work, we investigated the anaerobic decolorization of methyl orange (MO), a typical azo dye, by Shewanella oneidensis MR-1, which can use various organic and inorganic substances as its electron acceptor in natural and engineered environments. S. oneidensis MR-1 was found to be able to obtain energy for growth through anaerobic respiration accompanied with dissimilatory azo-reduction of MO. Chemical analysis shows that MO reduction occurred via the cleavage of azo bond. Block of Mtr respiratory pathway, a transmembrane electron transport chain, resulted in a reduction of decolorization rate by 80%, compared to the wild type. Knockout of cymA resulted in a substantial loss of its azo-reduction ability, indicating that CymA is a key c-type cytochrome in the electron transfer chain to MO. Thus, the MtrA-MtrB-MtrC respiratory pathway is proposed to be mainly responsible for the anaerobic decolorization of azo dyes such as MO by S. oneidensis.
Applied Microbiology and Biotechnology 08/2011; 93(4):1769-76. · 3.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A highly selective and sensitive LC-MS-MS method was developed and validated to quantify tiopronin in human plasma, using fudosteine as the internal standard (IS). L-Cysteine and 1,4-dithiothreitol (DTT) were used as the reducer and the stabilizer to release and stabilify tiopronin from a dimmer and mix forms with endogenous thiols in the treatment of plasma samples. After a simple liquid-liquid extraction with ethyl acetate in acidic condition, the post-treatment samples were analyzed on a C(18) column interfaced with a triple-quadruple tandem mass spectrometer using negative electrospray ionization. Methanol and water (40:60, v/v) were used as the isocratic mobile phase, with 0.2% formic acid and 1.0 mM tris (hydroxymethyl) aminomethane (Tris) in water. The method was validated to demonstrate the specificity, lower limit of quantification, accuracy and precision of measurements. The assay was linear over the concentration range 0.078-10 microg/mL. The correlation coefficients for the calibration curves ranged from 0.9980 to 0.9990. The intra- and inter-day precisions, calculated from quality control samples, were not more than 10.49%. The method was employed in a pharmacokinetic study after oral administration of 200 mg tiopronin tablets to 24 healthy volunteers.
[Show abstract][Hide abstract] ABSTRACT: In this study, a rapid, sensitive and reproducible liquid chromatography–tandem mass spectrometry method for the determination
of levonorgestrel in human plasma, was developed and validated. With a structural analogue norethindrone as the internal standard,
levonorgestrel was extracted from plasma using ethyl acetate. The organic layer was evaporated to dryness and the residue
was reconstituted in mobile phase. An aliquot of 20μL was chromatographically analyzed on a Phenomenex Luna C18 column with water and acetonitrile as the mobile phase. Selected reaction monitoring was specific for mass detection employing
positive electrospray ionization. The calibration standards were linear over the concentration range 0.625–40ngmL−1. The intra- and inter-day precision over the entire concentration range were less than 8.16%. The method was found to be
suitable for application to a pharmacokinetic study after oral administration of 1.5mg levonorgestrel tablet to 20 healthy
[Show abstract][Hide abstract] ABSTRACT: A simple and sensitive HPLC/MS/MS method was developed and evaluated to determine the concentration of ritodrine (RTD) in human plasma. Liquid-liquid extraction with ethyl acetate was employed as the sample preparation method. The structural analogue salbutamol was selected as the internal standard (IS). The liquid chromatography was performed on a Hanbon Sci. & Tech. Lichrospher CN (150 mm x 4.6 mm, i.d., 5 microm) column (Hanbon, China) at 20 degrees C. A mixture of 0.03% acetic acid and methanol (50:50, v/v) was used as isocratic mobile phase to give the retention time 3.60 min for ritodrine and 2.94 min for salbutamol. Selected reaction monitoring (SRM) in positive ionization mode was employed for mass detection. The calibration functions were linear over the concentration range 0.39-100 ng mL(-1). The intra- and inter-day precision of the method were less than 15%. The lower limit of quantification was 0.39 ng mL(-1). The method had been found to be suitable for application to a pharmacokinetic study after oral administration of 20mg ritodrine hydrochloride tablet to 18 healthy female volunteers. The half-life is 2.54+/-0.67 h.
Journal of Chromatography B 06/2008; 867(1):144-8. · 2.69 Impact Factor