Effect of permanganate oxidation on the photoreactivity of dissolved organic matter for photodegradation of typical pharmaceuticals.

Permanganate has been widely used in the remediation of contaminated water due to its relatively strong oxidation properties and ease of use. The ubiquitous dissolved organic matter (DOM) in natural waters causes a significant sink of permanganate in treatments, which further impacts the photoformation of reactive species and the removal of trace pollutants by DOM. Significantly, the effect of permanganate oxidation on the photoreactivity of DOM remains unknown. The present paper investigated for the first time the photophysical and photochemical properties variation of DOM from different sources after permanganate oxidation. Results showed that the permanganate oxidation caused a decrease in UV absorbance, fluorescence intensity, aromaticity, and molecular weight for all tested DOM samples, as well as photoformation rate of DOM triplet states (3DOM⁎), singlet oxygen (1O2), and hydroxyl radical (OH) under simulated sunlight. Quantum yield of 1O2 showed positively linear correlations with both triplet quantum yield coefficient (fTMP) and E2/E3 (ratio of absorbance at 254 and 365 nm) for all the DOM samples before and after permanganate oxidation. The quantum yield of OH exhibited no significant correlation with fTMP or E2/E3. Permanganate oxidation inhibited the DOM-photosensitized indirect photodegradation of pollutants that do not absorb sunlight (e.g., decreased by 15-29%). For the tested pollutants that undergo direct photolysis under sunlight, their photodegradation was promoted (e.g., increased by 1-19%) in the permanganate oxidized DOM solutions due to the decrease of light-screening effect by DOM. These findings suggest that permanganate oxidation affects the photoreactivity of DOM and the corresponding photochemical fate of organic pollutants in natural waters.

Montmorillonite promoted photodegradation of amlodipine in natural water via formation of surface complexes.

The photolysis of amlodipine (AML) as a ubiquitous pollutant in natural water has been extensively studied. Montmorillonite (MMT), a major component of suspended particles in surface aquifers, plays key roles in the natural transportation and transformation of organic contaminants in the environment. However, literature has scarcely focused on whether and how suspended particles affect the phototransformation of AML. This study systematically investigated the phototransformation behavior of AML in MMT suspensions under simulated sunlight. The results obtained showed that MMT significantly enhanced the photolysis of AML. The photodegradation of AML in 0.05 g/L MMT suspension reached 92.2 % after 3 h irradiation under the simulated sunlight. The photodecomposition followed the pseudo-first-order kinetic with a rate constant of 0.803 h-1 in the presence of 0.05 g/L MMT, which is about 19 times larger than that in the absence of MMT (0.0421 h-1). Further mechanistic investigation suggested that MMT accelerated the photolysis of AML by the formation of surface complexes between cationic amino groups of AML and the negatively charged sites on MMT surface, which greatly facilitated light absorption and electron transfer for the production of cationic radical AML+·. Meanwhile, the hydroxyl radicals generated by irradiated MMT also played an important role in the photocatalytic degradation of AML. The probable photodegradation pathways of AML in MMT suspension further supported the proposed mechanisms. The toxicity evaluation of phototransformation products of AML with ECOSAR program indicated that photolysis could reduce its potential threats. These findings reveal an important and previously overlooked phototransformation mechanisms of AML in the presence of MMT clays, which is of importance in assessing the environmental fate of other similar organic contaminants.

Formation and transformation of halonitromethanes from dimethylamine in the presence of bromide during the UV/chlorine disinfection.

Halonitromethanes (HNMs) is a typical class of nitrogenous disinfection byproducts with high toxicity. The effect of Br- on the formation and transformation of HNMs from dimethylamine (DMA) during the ultraviolet (UV)/chlorine disinfection has been investigated in current study. Results reveal that only chloronitromethane, dichloronitromethane and trichloronitromethane (TCNM) could be found during the UV/chlorine disinfection. Whereas in the presence of Br-, nine species of HNMs could be observed simultaneously. When Br- concentration increased from 0 to 15.0 mg L-1, the predominant species of HNMs were gradually changed from TCNM to dibromonitromethane and tribromonitromethane, which contributed to 23.37% and 31.07% of total HNMs concentration at 15 mg L-1 Br-, respectively. The presence of Br- not only shifted the chlorinated-HNMs (Cl-HNMs) towards brominated-HNMs (Br-HNMs) but also affected the dominant species and total concentration of HNMs. When Br- concentration was 4.0 mg L-1, the formation of HNMs decreased with the increase of pH from 6.0 to 8.0 and increased with the increase of free chlorine and DMA. When free chlorine concentration rose from 0.25 to 1.1 mmol L-1, Br-HNMs were shifted to Br(Cl)-HNMs and then to Cl-HNMs. According to the findings, possible formation and transformation pathways of HNMs from DMA were proposed in the presence of Br- during the UV/chlorine disinfection. Finally, it was proved that the effect of Br- on the trend of HNMs in real water was similar to that in deionized water, but higher HNMs concentrations and delayed peak time were observed in real water. This study can provide the scientific evidence and fundamental data for the applications of UV/chlorine disinfection in the treatment of water containing Br-.

Formation and enhanced photodegradation of chlorinated derivatives of bisphenol A in wastewater treatment plant effluent.

There are many reports on the detection and removal of emerging pollutants in the wastewater effluents, while the fate of their chlorinated derivatives generated during chlorination is not well understood. Here we investigated the photodegradation of chlorinated derivatives of bisphenol A (CDBPAs), mainly including 3-chlorobisphenol A, 3,3'-dichlorobisphenol A, 3,5-dichlorobisphenol A, 3,3',5-trichlorobisphenol A, and 3,3',5,5'-tetrachlorobisphenol A, under simulated sunlight. Distinct from BPA, CDBPAs underwent rapid direct photodegradation due to a pronounced bathochromic shift of UV absorption. The photodegradation of CDBPAs was significantly enhanced by effluent organic matter (EfOM) from the wastewater effluent. A series of quenching experiments and laser flash photolysis analysis verified the contribution of triplet states of EfOM (3EfOM∗) for the indirect photodegradation of CDBPAs with rate constant of ∼109 M-1 s-1. Both direct and EfOM-induced indirect photodegradation of CDBPAs increased with a higher degree of chlorination. Furthermore, high-resolution mass spectrometry showed similar photoproducts for direct and indirect photodegradation of CDBPAs, mainly ascribed to the cleavage of C-Cl bond and hydroxylation with further cleavage of the benzene ring. The estrogenic activity of the photoproducts was diminished. These findings suggest that photodegradation is an important pathway for the removal and detoxication of CDBPAs from effluents and receiving natural waters under sunlight.

Singlet oxygen production abilities of oxidated aromatic compounds in natural water.

Singlet oxygen (1O2) is well known to be formed through energy transfer from excited state organic matters to O2, playing an important role in the transformations of contaminants. However, the contribution of small oxidated aromatic compounds (OACs) to the production of 1O2 in surface water is unclear. In this study, 28 OACs were selected to investigate the correlations between their photochemical production abilities of 1O2 and molecular structures. Our results showed that the steady-state concentrations and quantum yields of 1O2 (Φ1O2) generated by OACs were in the range of 7.0 × 10-14-1.4 × 10-12 M and 2.2 × 10-4-4.7 × 10-2, respectively, indicating that the photochemical production abilities of 1O2 by OACs varied greatly with types and positions of functional groups on the molecule. More importantly, the observed photochemical production of 1O2 was most notable in cases of molecules containing -OCH3 group and benzoquinone. A good quantitative structure-property relationship model was established between 1O2 producing ability, energy of the lowest unoccupied molecular orbitals (ELUMO) and the most positive net charge of hydrogen atoms (qH+) of OACs. In addition, the role of 1O2 produced by 2, 6-dimethoxy-1, 4-benzoquinone, the OAC with the highest Φ1O2, in the photodegradation of organic contaminants was validated by the enhanced degradation of atorvastatin under simulated sunlight, suggesting that OACs ubiquitously existed in surface water may greatly affect the fate and ecological risks of organic contaminants.

The enhanced visible-light-driven antibacterial performances of PTCDI-PANI(Fe(III)-doped) heterostructure.

The development of visible-light-responsive photocatalysts with organic semiconductors is considered as an important and promising way to solve the energy crisis and environmental pollution. In this work, PTCDI and PTCDI-PANI(Fe(III)-doped) heterostructure were prepared through radical polymerization and modified amidation reaction. They could be used as visible-light-driven photocatalysts for the treatment of medical wastewater containing Staphylococcus aureus and E. coli bacteria. The as-prepared PTCDI-PANI(Fe(III)-doped) exhibited comparably higher photocatalytic activity beyond PTCDI. Under the irradiation of visible light, the PTCDI-PANI(Fe(III)-doped) showed optimized sterilization efficiencies towards E. coli and Staphylococcus aureus bacteria, which was 95.8% and 99.3%, respectively. The enhanced photo-induced antibacterial effect by PANI(Fe(III)-doped)-grafting was mainly attributed to: (1) PANI has a narrow band gap of 2.8 eV; (2) The relatively higher conduction band position (-2.1 eV) of PANI promotes the reaction of O2+e－⟶·OH; (3) The strengthened junctions of amide bond between PTCDI and PANI improve the separation efficiency of photogenerated electron-hole pairs; (4) The relatively rougher surface of PTCDI-PANI comparing with PTCDI improves the bio-surface interactions or bacterial adhesion; (5) Fe(III)-doping acts as a conducting tunnel and promotes the charge transfer between PANI and PTCDI.

Photolysis of bis(2-ethylhexyl) phthalate in aqueous solutions at the presence of natural water photoreactive constituents under simulated sunlight irradiation.

The photolysis of bis(2-ethylhexyl) phthalate (DEHP) under simulated sunlight in the presence of the natural water photoreactive constituents was investigated. The presence of nitrate or ferric ions facilitated the photodegradation of DEHP via oxidation by generation of •OH. The fulvic acids (FAs), at low concentrations, promoted the photolysis of DEHP via energy transfer from the photoreaction-generated 3FA*. However, the DEHP photolysis was inhibited with high concentrations of FAs since the excess FAs at the surface of solution could act as light screening agents to keep FAs in bulk solution from the light irradiation, further reducing the 3FA* generation. When low concentrations of FAs and chloride ions coexist, the reactive chloride species Cl• and Cl2•- could generate via energy transfer from 3FA* to chloride ions and react with DEHP to enhance its degradation. Furthermore, the direct and •OH-initiated DEHP photodegraded intermediates and end products were identified by HPLC-MS2 and its corresponding photolysis pathways were proposed.

Mechanistic Insight into the Effect of Metal Ions on Photogeneration of Reactive Species from Dissolved Organic Matter.

The photogeneration of reactive species (RS) from dissolved organic matter (DOM) exhibits a great impact on the attenuation of pollutants in natural waters. However, the effect of metal ions on the photogeneration of excited triplet-state DOM (3DOM*), singlet oxygen (1O2), and hydroxyl radical (•OH) by effluent organic matter (EfOM), fulvic acid (FA), and humic acid (HA) is poorly understood. Here, we provided the first evidence that the quenching of 3DOM* was positively correlated with the complexation capacity of metal ions with DOM. Generally, the paramagnetic metal ions (Cr3+, Mn2+, Fe3+, and Cu2+) exhibited higher conditional stability constants (log KML) with DOM and stronger inhibition for RS than the others (Mg2+, Ca2+, Al3+, and Zn2+). For DOM of different sources, the metal binding capacity increased in the order of EfOM < HA < FA and the humic substances were more susceptible to metal ions. The inhibition was attributed to both static and dynamic quenching of 3DOM* by metal ions. The dynamic quenching rate constants of metal ions for 3DOM* were estimated as ∼109 M-1 s-1, which was positively related to the corresponding log KML. These findings highlight crucial links between metal-DOM complexation and 3DOM* quenching and, consequently, the inhibition of RS.

Photogeneration of hydroxyl radical in Fe(III)-citrate-oxalate system for the degradation of fluconazole: mechanism and products.

The photochemical role of Fe(III)-citrate complex is significant in natural waters due to its ubiquitous existence and excellent photoreactivity at near neutral pH. Although there are many reports on the photoinduced degradation of pollutants in the Fe(III)-citrate system, the optimum pH for its photoreactivity is yet not clearly understood. Here, for the first time, we demonstrated that the optimum pH was 5.5 for the photoproduction of •OH in the Fe(III)-citrate system via kinetics modeling based on the steady-state approximation. According to the experimental results, the •OH photoproduction increased with increasing pH until 5.5 and then decreased in Fe(III)-citrate solution, which agreed well with the prediction trend of kinetic modeling. The effect of the common ligand oxalate on the photoreactivity of Fe(III)-citrate system was also investigated. The addition of oxalate promoted the photoproduction of •OH in Fe(III)-citrate solutions, and the measured [•OH]ss increased with oxalate concentration under a fixed Fe(III)-to-citrate ratio. Little synergistic effect exists in Fe(III)-citrate-oxalate system at pH 4.0-5.5. In contrast, an appreciable synergistic effect was observed at near neutral pH (6.0-8.0). Higher oxalate-to-citrate ratio facilitated the synergistic effect. Furthermore, antifungal drug fluconazole could be removed efficiently in the Fe(III)-citrate-oxalate system. The photodegradation kinetics also verified the optimum pH of Fe(III)-citrate system and synergistic effect of oxalate. By LC-ESI-MS/MS analyses, the photoproducts of fluconazole in the Fe(III)-citrate-oxalate system were identified and the reaction mechanism involving hydroxylation substitution and subsequent cleavage of heterocyclic amine was proposed. These findings suggest that Fe(III)-citrate exhibits best photoreactivity at pH 5.5, and the coexistence of reactive ligands will enhance its photoreactivity at circumneutral pH, indicating potential application in wastewater treatment via addition of appropriate citrate and co-ligands.

Graphene oxide based molecularly imprinted polymers modified with ß-cyclodextrin for selective extraction of di(2-ethylhexyl) phthalate in environmental waters.

Graphene oxide based molecularly imprinted polymers modified with ß-cyclodextrin were prepared as solid-phase extraction column sorbents for specific recognition and sensitive detection of di(2-ethylhexyl) phthalate in water samples. The morphology and composition of synthesized sorbents were characterized by scanning electron microscopy, thermo-gravimetric analysis, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The conditions affecting the performance of extraction procedures such as desorption solvent types and volume, sample pH and volume were investigated. The loading capacity (8.2 µg/mg) of the prepared sorbents increased eight times after modification with ß-cyclodextrin. The developed extraction procedures coupled to high-performance liquid chromatography exhibited good linearity (0.2-500 µg/L), low limit of detection (0.052 µg/L), and good precision (relative standard deviation˂5.7%) under optimized conditions. The developed solid-phase extraction technique with prepared sorbents has been successfully applied in extracting trace di(2-ethylhexyl) phthalate from real natural waters with high efficiency, good selectivity, and desirable recoveries.

Photodegradation of amitriptyline in Fe(III)-citrate-oxalate binary system: Synergistic effect and mechanism.

Fe(III) and carboxylic acids are ubiquitous in surface water and atmospheric water droplets. Numerous documents have reported the photochemistry of Fe(III)-carboxylate complexes, typically including Fe(III)-oxalate and Fe(III)-citrate. Our previous study preliminarily showed that oxalate enhances the photoreactivity of Fe(III)-citrate system. Here, we further investigate the synergistic effect of Fe(III)-citrate-oxalate binary system at different conditions with pharmaceutical amitriptyline (AMT) as the model pollutant. In the Fe(III)-oxalate system, the photodegradation of AMT decreased with increasing pH from 3.0 to 8.0. In the Fe(III)-citrate system, the optimal pH for AMT degradation is around 5.0 in the same pH range. For the Fe(III)-citrate-oxalate system, the photodegradation of AMT decreased with increasing pH, indicating the combined effect of both oxalate and citrate on the photoreactivity. The addition of oxalate to the Fe(III)-citrate system markedly accelerated the photodegradation of AMT. The Fe(III)-carboxylate binary system exhibited excellent photoreactivity and up to 90% AMT was removed after 30 min at pH 6.0 with Fe(III)/citrate/oxalate ratio of 10:150:500 (µM). Synergistic effect was observed in Fe(III)-citrate-oxalate binary system in the pH range of 5.0-8.0. The presence of oxalate promoted the depletion of citrate in the Fe(III)-citrate system. The higher concentration ratios of oxalate to citrate facilitated the synergistic effect in the Fe(III)-citrate-oxalate system. By LC-MS analyses, a possible pathway of AMT degradation was proposed based on hydroxyl radicals (OH) mechanism. This finding could be helpful for the better understanding of synergistic mechanism of Fe(III)-citrate-oxalate binary complexes, which will be of great potential application in environmental photocatalysis at near neutral pH.

Ultraviolet absorption redshift induced direct photodegradation of halogenated parabens under simulated sunlight.

As disinfection by-products of parabens, halogenated parabens are frequently detected in aquatic environments and exhibit higher persistence and toxicity than parabens themselves. An interesting phenomenon was found that UV absorption redshift (∼45 nm) occurs after halogenation of parabens at circumneutral pH, leading to overlap with the spectrum of terrestrial sunlight. This work presents the first evidence on the direct photodegradation of seven chlorinated and brominated parabens under simulated sunlight. These halogenated parabens underwent rapid direct photodegradation, distinguished from the negligible degradation of the parent compounds. The photodegradation rate depended on their forms and substituents. The deprotonation of halogenated parabens facilitated the direct photodegradation. Brominated parabens exhibited higher degradation efficiency than chlorinated parabens, and mono-halogenated parabens had higher degradation than di-halogenated parabens. The pseudo-first-order rate constants (kobs) for brominated parabens (0.075-0.120 min-1) were approximately 7-fold higher than those of chlorinated parabens (0.011-0.017 min-1). A quantitative structure-activity relationship (QSAR) model suggested that the photodegradation was linearly correlated with the C-X bond energies, electronic and steric effects of halogen substituents. The photodegradation products were identified using QTOF-MS analyses and a degradation pathway was proposed. The yeast two-hybrid estrogenicity assay revealed that the estrogenic activities of the photoproducts were negligible. These findings are important for the removal of halogenated parabens and predictions of their fate and potential impacts in surface waters.

Occurrence, endocrine-related bioeffects and fate of bisphenol A chemical degradation intermediates and impurities: A review.

In recent decades, increasing attention has been directed toward the effects of bisphenol A (BPA) as an environmental pollutant, primarily due to its demonstrated endocrine-disruptive effects. A growing body of evidence indicates that many BPA derivatives also exhibit endocrine activity and other adverse biological properties. A review of the published literature was performed to identify BPA degradation intermediates resulting from chemical degradation processes of BPA, as well as BPA's associated co-pollutants. Products of biological metabolism were not included in this study. Seventy-nine chemicals were identified. Of these chemicals, a subset - those containing two 6-membered aromatic rings connected by a central ring-linking carbon - was identified, and a further literature review was conducted to identify demonstrated biological effects associated with the chemicals in this subset. The objectives of this review were to assess the potential risks to human and environmental health associated with BPA derivatives, characterize our current understanding of BPA's degradation intermediates and co-pollutants, and aid in the identification of compounds of interest that have received insufficient scrutiny.

Photosensitized Degradation of Amitriptyline and Its Active Metabolite Nortriptyline in Aqueous Fulvic Acid Solution.

Amitriptyline is a frequently prescribed tricyclic antidepressant. Although amitriptyline and its active metabolite, nortriptyline, have been widely detected in natural waters, their environmental fate due to photodegradation is poorly understood. Here we describe a study conducted to investigate the photodegradation of amitriptyline and its active metabolite under simulated sunlight. Neither amitriptyline nor nortriptyline underwent direct photodegradation, but rapid photosensitized degradation did occur in fulvic acid (FA) solutions. The photodegradation of amitriptyline and nortriptyline followed pseudo-first-order kinetics with rate constants 0.24 and 0.16 h, respectively, at pH 8.0 in air-saturated FA solutions. The photodegradation of the substrates increased markedly with pH. The deprotonation of amitriptyline and nortriptyline facilitated the availability of nonbonding electrons on nitrogen (N-electrons). The excited triplet state of FA (FA*) was verified as the main reactive species responsible for the photosensitized degradation. An electron transfer mechanism for the interaction between substrates and FA* was proposed on the basis of a series of quenching experiments, kinetic model and photoproducts determination. Demethylation at the α-carbon of amine and hydroxylation were two primary photochemical processes initiated by the electron transfer reaction in the air-saturated FA solution; these were followed by generation of demethyl amine and mono-hydroxylation isomers. Our results suggest that indirect photodegradation is an important elimination process for amitriptyline and its active metabolite in natural waters.

A rapid hydrophilic interaction liquid chromatographic determination of glimepiride in pharmaceutical formulations.

Glimepiride is one of the most widely prescribed antidiabetic drugs and contains both hydrophobic and hydrophilic functional groups in its molecules, and thus could be analyzed by either reversed-phase high performance liquid chromatography (HPLC) or hydrophilic interaction liquid chromatography (HILIC). In the literature, however, only reversed-phase HPLC has been reported. In this study, a simple, rapid and accurate hydrophilic interaction liquid chromatographic method was developed for the determination of glimepiride in pharmaceutical formulations. The analytical method comprised a fast ultrasound-assisted extraction with acetonitrile as a solvent followed by HILIC separation and quantification using a Waters Spherisorb S5NH2 hydrophilic column with a mobile phase consisting of acetonitrile and aqueous acetate buffer (5.0 mM). The retention time of glimepiride increased slightly with decrease of mobile phase pH value from 6.8 to 5.8 and of acetonitrile content from 60% to 40%, indicating that both hydrophilic, ionic, and hydrophobic interactions were involved in the HILIC retention and elution mechanisms. Quantitation was carried out with a mobile phase of 40% acetonitrile and 60% aqueous acetate buffer (5.0 mM) at pH 6.3, by relating the peak area of glimepiride to that of the internal standard, with a detection limit of 15.0 µg/L. UV light absorption responses at 228 nm were linear over a wide concentration range from 50.0 µg/L to 6.00 mg/L. The recoveries of the standard added to pharmaceutical tablet samples were 99.4-103.0% for glimepiride, and the relative standard deviation for the analyte was less than 1.0%. This method has been successfully applied to determine the glimepiride contents in pharmaceutical formulations.

Role of humic substances in the photodegradation of naproxen under simulated sunlight.

Humic substances (HS) including humic acid (HA) and fulvic acid (FA) are ubiquitous in the natural waters. Although numerous studies documented their role in photodegradation of organic pollutants, the competitive effects of photosensitization and light-screening of HS on the photodegradation of pollutants are not yet clear. In this work, the role of HS in the photodegradation of the pharmaceutical naproxen (NP) was studied under simulated sunlight. The direct photodegradation quantum yield of NP in deionized water was 2.1 × 10-2, and the apparent quantum yields for photosensitized degradation of NP in the presence of FA and HA were 2.3 × 10-4 and 2.6 × 10-5, respectively. Both direct and photosensitized photodegradation decreased with increasing pH, consistent with the trend of singlet oxygen (1O2) reaction rate constants of NP. HA inhibited the photodegradation of naproxen thoroughly. In contrast, FA accelerated the photodegradation of NP at lower substrate concentration and light intensity, and vice versa. Direct photodegradation of NP declined sharply with spectral radiation attenuation of UV region, when HS-mediated photosensitization predominantly accounted for the photodegradation. The direct photodegradation was ascribed to decomposition of excited triplet state of naproxen (3NP∗) and self-sensitization effect involving 1O2. The FA-mediated photodegradation was mainly attributed to 1O2 oxidation in aerated solution. These findings are important for assessing the competitive effects of humic substances on the photodegradation of pollutants under various conditions in natural waters.

Occurrence and photodegradation of methylmercury in surface water of Wen-Rui-Tang River network, Wenzhou, China.

The spatial distribution and seasonal variations of methylmercury (MeHg) in Wen-Rui-Tang (WRT) River network were investigated by monitoring the MeHg concentrations in surface water samples collected from 30 sites across the river network over four seasons. Detection frequencies and concentrations of MeHg were generally higher in January, indicating that low sunlight irradiation, wind speed, and temperature conditions might enhance the persistence of MeHg in surface water. The MeHg levels varied with sampling locations, with the highest concentrations being observed in the industrial area especially around wastewater outfall, revealing that the mercury contamination in WRT River mainly comes from the industrial wastewater. Photodegradation of MeHg in WRT River surface water and the effects of natural constituents such as fulvic acid (FA), ferric ions (Fe3+), nitrate (NO3-), and dissolved oxygen on the MeHg photodegradation in aqueous solutions were studied under the simulated sunlight. The experimental data indicated that the indirect photodecomposition of MeHg occurred in WRT River surface water. Photodegradation of MeHg in FA solution was initiated by triplet 3FA* or MeHg-FA* via electron transfer interaction under light irradiations. The Fe3+ and NO3- can absorb light energy to produce ·OH and enhance the photochemical degradation of MeHg. The MeHg photodecompositions in FA, nitrate, and Fe3+ solutions were markedly accelerated after removing the dissolved oxygen.

Characterization of free and conjugated phenolic compounds in fruits of selected wild plants.

A gas chromatography-mass spectrometric (GC-MS) method was utilized for the separation, and systematic characterization of phenolic compounds as trimethylsilyl derivatives in fruits of wild plants including Olive, Jujube and Common Fig. Both the free and conjugate phenolic acids (rarely determined before and several are reported first time here) were characterized. A baseline separation of the 20 phenolics was achieved in 25 min with standard calibration curves linear over the concentration range from the detection limits to 20 µg/mL. Total of fourteen phenolic acids were identified in wild Olive fruit, eight in wild Jujube fruit and ten in wild Common Fig fruit, out of which 2,4-dihydroxybenzoic acid and trans-cinnamic acid were dominant in these fruits with concentration of 87.02, 5.25 and 14.16 mg/kg and 32.43, 5.77 and 11.70 mg/kg (dry weight), respectively. The results of this study support the utilization of the tested wild fruits as a potential source of valuable phenolics for functional food and nutraceutical applications.

Determination of creatinine, uric and ascorbic acid in bovine milk and orange juice by hydrophilic interaction HPLC.

Creatinine (Cr), uric (UA) and ascorbic acid (AA) are common constituents in human fluids. Their abnormal concentrations in human fluids are associated with various diseases. Thus, apart from the endogenous formation in human body, it is also important to examine their sources from food products. In this study, a rapid and accurate HILIC method was developed for simultaneous determination of Cr, UA and AA in bovine milk and orange juice. Milk samples were pretreated by protein precipitation, centrifugation and filtration, followed by HPLC separation and quantification using a Waters Spherisorb S5NH2 column. The developed method has been successfully applied to determine the concentration of UA, AA and Cr in milk and fruit juice samples. The milk samples tested were found to contain UA and creatinine in the concentration range of 24.1-86.0 and 5.07-11.2 µg mL(-1), respectively. The orange juices contain AA over 212 µg mL(-1).

Simultaneous identification and quantification of 4-cumylphenol, 2,4-bis-(dimethylbenzyl)phenol and bisphenol A in prawn Macrobrachium rosenbergii.

Bisphenol A (BPA), 4-cumylphenol (4-CP) and 2,4-bis-(dimethylbenzyl)phenol (2,4-DCP) are all high production volume chemicals and widely used in plastic and other consumer products. During the past two decades, BPA has attracted a great deal of scientific and public attention due to its presence in the environment and estrogenic property. Although 4-CP and 2,4-DCP are much more estrogenic and toxic than BPA, little information is available about their occurrence and fate in the environment. In this study, a rapid, selective, accurate and reliable analytical method was developed for the simultaneous determination of 4-CP, 2,4-DCP and BPA in prawn Macrobrachium rosenbergii. The method comprises an ultrasound-accelerated extraction followed by capillary gas chromatographic (GC) separation. The detection limits range from 1.50 to 36.4 ng kg(-1) for the three alkylphenols. The calibration curves are linear over the concentration range tested with the coefficients of determination, R(2), greater than 0.994. The developed method was successfully applied to the simultaneous determination of 4-CP, 2,4-DCP and BPA in prawn samples. The peak identification was confirmed using GC-MS. Bisphenol A, 2,4-bis-(dimethylbenzyl)phenol and 4-cumylphenol were found in prawn samples in the concentration ranges of 0.67-5.51, 0.36-1.61, and 0.00-1.96 ng g(-1) (wet weight), respectively. All relative standard deviations are less than 4.8%. At these environmentally relevant concentration levels, 4-CP, 2,4-DCP and BPA may affect the reproduction and development of aquatic organisms, including negative influence on crustaceans' larval survival, molting, metamorphosis and shell hardening. This is the first study reported on the occurrence of 4-CP, 2,4-DCP and BPA in prawn M. rosenbergii.