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Despite the possible occurrence of metal nanoparticles in the environment due to the discharge of engineered nanoparticles and the natural transformation of metal ions into metal nanoparticles, little is known about the transformation mechanism, fates, behaviors, and effects of these nanoparticles in the environment. Here, we show that dissolved organic matter (DOM) in environmental waters can mediate the reduction of ionic Ag and Au to their metallic nanoparticles under natural sunlight, suggesting that this process may be general for metals with high reduction potential. We demonstrated that the reduction was mediated by superoxide from photoirradiation of the phenol group in DOM, and the dissolved O(2) significantly enhanced the formation of Ag nanoparticles. These results imply that previous knowledge about O(2)-induced dissolution and its effect on persistence of Ag nanoparticles should be reconsidered in a sunlit DOM-rich aqueous environment. This study can also shed light on understanding possible natural sources of Ag and Au nanoparticles in the aquatic environment, which is possibly critical in the supergene enrichment of Ag and Au.

Mercury methylation and/or demethylation have been observed in several compartments [soil (saturated soils covered by standing water), floc, periphyton, and water] of the Everglades, a wetland with mercury as one of the major water quality concerns. However, it is still unclear which compartment is the major source or sink due to the lack of estimation and comparison of the net methylmercury (MeHg) production or degradation in these compartments. The lack of this information has limited our understanding of Hg cycling in this ecosystem. This study adopted a double stable isotope (Hg-199(2+) and (MeHg)-Hg-201) addition technique to determine the methylation/demethylation rate constants and the net MeHg production rates in each compartment. This study improved the previous models for estimating these parameters by (1) taking into account the difference between newly input and ambient mercury in methylation/demethylation efficiency and (2) correcting the contribution of photodemethylation to (MeHg)-Hg-199 concentration when calculating methylation rates in water. The net MeHg production rate in each compartment was then estimated to identify the major sources and sinks of MeHg. The results indicate that these improvements in modeling are necessary, as a significant error would occur otherwise. Soil was identified to be the largest source of MeHg in the Everglades, while the floc and water column were identified as the major sinks. The role of periphyton varies, appearing to be a source in the northern Everglades and a sink in the southern Everglades. Soil could be the largest source for MeHg in the water column, while methylation in periphyton could also contribute significantly in the northern Everglades.

A bioactive peptide Arg–Val–Pro–Ser–Leu (RVPSL) obtained from egg white protein was characterized by LC-MS and further chemically synthesized by the Fmoc solid phase method and investigated in terms of its angiotensin converting enzyme (ACE)-inhibitory activity, antioxidant property, and anticoagulation activity, as well as its stability in a simulated gastrointestinal digestion. The peptide exhibited an ACE-inhibitory activity with an IC50 value of 20 μM. Also, the peptide could efficiently quench the (1,1)-diphenyl-2-picrylhydrazyl free radicals and exhibit high anticoagulation activity with a complete inhibition at 100 mM. Moreover, the peptide has a good stability against protease digestion. These results suggest that the peptide RVPSL may have potential to be used in nutraceuticals and functional food. Practical Application: The present research revealed a novel multifunctional peptide hydrolyzed from egg white protein. The peptide RVPSL was not only able to block the amplification of the coagulation cascade, but also able to inhibit ACE activity.

The objectives of this study were to identify novel peptides from albumin, and to evaluate and validate the anti-diabetic activity of peptides against α-glucosidase and α-amylase. In the research, albumin hydrolysate was purified and identified, tandem MS was adapted to characterise the amino acid sequences of peptides from the hydrolysate. In addition, anti-diabetic effects of the peptides with α-glucosidase and α-amylase inhibitory activity have been performed. The present work found eight novel peptides from albumin. Results also suggested that peptide KLPGF had α-glucosidase inhibitory activity with an IC(50) of 59.5±5.7μmoll(-1) and α-amylase inhibitory activity with an IC(50) of 120.0±4.0μmoll(-1). In conclusion, the results revealed that the peptide KLPGF was a potential anti-diabetic inhibitor.

High-intensity pulsed electric fields (PEF) was applied to treat beer waste brewing yeasts (BWBY) to improve the permeability of yeast cell membrane in order to extract trehalose. Several independent variables such as pH (3 to 7), electric field strength (0 to 50 kV/cm), pulse numbers (0 to 10) and liquidsolid ratio (20: 1 to 60: 1) were investigated. The optimal parameters were obtained by one-factor-at-atime (OFAT) experiment and quadratic regression orthogonal design. The results showed that under the conditions of electric fields intensity of 19.97 kV/cm, pulse number of 6, and liquid-solid ratio of 30:1, the extraction rate of trehalose could reach 2.635%. In addition, the extraction efficiency of trehalose treated by PEF was compared with other two trehalose extraction methods, example microwave and ultrasound, and the efficiency of PEF was found to be 103.15 μg/s; it was 15.96 times higher than microwave and 34.08 times higher than ultrasound. This demonstrated that the PEF could be regarded as a promising technique for bio-material extraction.Key words: High-intensity pulsed electric field (PEF), Beer waste brewing yeast (BWBY), Trehalose, Regression model.

The methylation of inorganic Hg by anaerobic bacteria in aquatic environments is considered to be the major pathway for methylmercury (MeHg) production. However, recent research has suggested that abiotic or chemical methylation by humic substances and other low-molecular-weight organic compounds in natural environments is also possible. Here, the aqueous photo-transformation of Hg(2+) to organomercurials was investigated in the presence of ketones, aldehydes and low molecular weight organic acids under UV irradiation. MeHg and/or ethylmercury (EtHg) were identified as the main organomercurial products by multiple analytical techniques, including chromatography-atomic spectrometry and molecular mass spectrometry and further confirmed by stable isotope tracer experiments. The yield of organomercurials was markedly influenced by pH, NaCl concentration, alkylation donor concentration and the presence of chelating ligands in the aqueous solution. Electron paramagnetic resonance spectrometry demonstrated that the radical reaction was not the predominating alkylation pathway, although methyl radicals were detected in the photo-alkylation procedure. A mechanism based on intra-molecular alkyl transfer in the Hg(2+)-low-molecular-weight organic compound complex is proposed. The present work helps us better understand of MeHg and EtHg photo-generation in natural environments.

The rapid growth in commercial use of silver nanoparticles (AgNPs) will inevitably increase silver exposure in the environment and the general population. As the fate and toxic effects of AgNPs is related to the Ag(+) released from AgNPs and the transformation of Ag(+) into AgNPs, it is of great importance to develop methods for speciation analysis of AgNPs and Ag(+). This study reports the use of Triton X-114-based cloud point extraction as an efficient separation approach for the speciation analysis of AgNPs and Ag(+) in antibacterial products and environmental waters. AgNPs were quantified by determining the Ag content in the Triton X-114-rich phase with inductively coupled plasma mass spectrometry (ICPMS) after microwave digestion. The concentration of total Ag(+), which consists of the AgNP adsorbed, the matrix associated, and the freely dissolved, was obtained by subtracting the AgNP content from the total silver content that was determined by ICPMS after digestion. The limits of quantification (S/N = 10) for antibacterial products were 0.4 μg/kg and 0.2 μg/kg for AgNPs and total silver, respectively. The reliable quantification limit was 3 μg/kg for total Ag(+). The presence of Ag(+) at concentrations up to 2-fold that of AgNPs caused no effects on the determination of AgNPs. In the cloud point extraction of AgNPs in antibacterial products, the spiked recoveries of AgNPs were in the range of 71.7-103% while the extraction efficiencies of Ag(+) were in the range of 1.2-10%. The possible coextracted other silver containing nanoparticles in the cloud point extraction of AgNPs were distinguished by transmission electron microscopy (TEM), scanning electron microscopy (SEM)- energy dispersive spectroscopy (EDS), and UV-vis spectrum. Real sample analysis indicated that even though the manufacturers claimed nanosilver products, AgNPs were detected only in three of the six tested antibacterial products.

Human exposure to toxic heavy metals via the food chain is of increasing concern. In the present study, the effects of soil type and genotype on variation in arsenic (As) concentrations of different organs were investigated by using nine rice cultivars grown in two soils, with two levels of As contamination. There were significant genotypic differences (P0.05) in As concentrations of all organs, and As concentrations of polished grain were significantly affected by genotype and soil type. The As concentration in polished grain was higher in red paddy soil under As treatment, with range from 0.24 to 1.03 mg kg(-1), and the As concentration of three cultivars exceeded the concentration of Chinese Food Hygiene Standard (0.7 mg kg(-1)). The As concentrations in stems, leaves and polished grain were all significantly and positively correlated. The As concentrations in polished grain were positively and significantly (P0.01) correlated with As root-grain translocation factor. The results indicated that As concentration in grain was partially governed by As uptake and the transfer of As from root to grain. The grain As concentration of the nine cultivars was significantly correlated between the two soil types at different levels of As contamination. Some genotypes, such as japonica rice (e.g. Ning jing 1 and Nan jing 32) had consistently low grain As concentrations. The results suggest the possibility of breeding the As rice cultivars to produce grain for safe consumption from soils with slight and moderate levels of As.

Egg white protein powder was hydrolyzed by three proteases-alcalase, trypsin, and pepsin-to produce antioxidant peptides. Three kinds of hydrolysates were prepared under optimal enzymatic parameters that were obtained from the preliminary one-factor-at-a-time test and response surface methodology. Thereafter, three enzymatic hydrolysates were sequentially fractionated by ultrafiltration membranes in cut-off MW of 30, 10, and 1 kDa, and tested in terms of their reducing power (RP). Effects of high-intensity pulsed electric field (PEF) were further investigated on the antioxidant peptides to improve their activities.Alcalase hydrolysates possessed stronger RP ability than the other two hydrolysates, particularly for the fraction within1 kDa. After PEF treatment, this fraction showed an improvement of RP ability within 4 h; however, the effects were reversible. High-performance liquid chromatographic analysis showed some MW changes of PEF-treated sample compared with control.Among the three kinds of proteases, alcalase could be regarded as the most appropriate enzyme for preparation of bioactive peptide from egg white protein, with the best antioxidant activity. Also, PEF showed some effects on the peptide and could be further applied to improve its antioxidant activity.

BACKGROUND: Corn silk is a traditional Chinese herbal medicine, which has been widely used for treatment of some diseases. In this study the effects of pulsed electric field on the extraction of polysaccharides from corn silk were investigated. RESULTS: Polysaccharides in corn silk were extracted by pulsed electric field and optimized by response surface methodology (RSM), based on a Box–Behnken design (BBD). Three independent variables, including electric field intensity (kV cm−1), ratio of liquid to raw material and pulse duration (µs), were investigated. The experimental data were fitted to a second-order polynomial equation and also profiled into the corresponding 3-D contour plots. Optimal extraction conditions were as follows: electric field intensity 30 kV cm−1, ratio of liquid to raw material 50, and pulse duration 6 µs. Under these condition, the experimental yield of extracted polysaccharides was 7.31% ± 0.15%, matching well with the predicted value. CONCLUSION: The results showed that a pulsed electric field could be applied to extract value-added products from foods and/or agricultural matrix. Copyright © 2011 Society of Chemical Industry

In order to develop an automatic and rapid detection method for enumeration of total bacteria in juice, biomimetic pattern recognition and machine vision were employed. The characteristic data, such as shape, texture and color features, were acquired by using the machine vision technology from bacteria images in varieties of juice. Based on multi-weight higher order neuron network, the recognition models were established which can achieve the imitation of human learning, memorizing and judging. By applying the principle of statistics, the detection results of new method showed no difference, compared with the traditional method in apple juice, tomato juice and carrot juice. The new method simplifies experimental preparation and shortens judgment time, especially in sample test on the spot and monitoring production site. Moreover, by using this rapid detection method, total bacteria counts in samples could be accurately enumerated within 1 h, which was much less than 24-48 h by using the traditional method.

A few studies have reported the occurrence of monoethylmercury (CH(3)CH(2)Hg(+)) in the natural environment. but further verification is needed due to the lack of direct evidence and/or uncertainty in analytical procedures. Various analytical techniques were employed to verify the occurrence of CH(3)CH(2)Hg(+) in soil of the Florida Everglades The identity of CH(3)CH(2)Hg(+) in Everglades soil was clarified, for the first time, by GC/MS. The employment of the recently developed aqueous phenylanon-purge-and-trap-GC coupled with ICPMS confirmed that the detected CH(3)CH(2)Hg(+) was not a misidentification of CH(3)SHg(+). Stable Isotope-tracer experiments further indicated that the detected CH(3)CH(2)Hg(+) indeed originated from Everglades soil and was not an analytical artifact All these evidence clearly confirmed the occurrence of CH(3)CH(2)Hg(+) in Everglades soil, presumably as a consequence of ethylation occurring in this wetland The prevalence of CH(3)CH(2)Hg(+) in Everglades soil suggests that ethylation could play an important role in the biogeochemical cycling of Hg (C) 2010 Elsevier Ltd. All rights reserved.

A comprehensive method for simultaneously detecting species of arsenic and selenium including arsenite (As(III)), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenate (As(V)), selenocystine (SeCys), selenomethionine (SeMet) and selenate (Se(IV)) was developed with high performance liquid chromatography-hydride generation-double channel atomic fluorescence spectrometry (HPLC-HG-AFS). An anion-exchange column (PRP-X100) with eluent of 10 mmol/L NH4H2PO4 containing 2.5% (v/v) methanol was employed to separate these species within 12 min. The detection limits of As(III), DMA, MMA, As(V), SeCys, SeMet and Se(IV) were 1, 3, 2, 3, 4, 18 and 3 microg/L (200 microL of injection), respectively. The relative standard deviations in five independent determinations varied from 1.9% to 6.1% for arsenic and selenium species at the concentration levels of 100 and 300 microg/L. The proposed method was applied to analyze the selenium yeast tablet and human urine samples. The recoveries from spiked selenium yeast tablet and urine samples ranged from 88% to 105% and from 83% to 108%, respectively. The results showed that this method can be used for determining arsenic and selenium species in urinary metabolites and drug samples in daily analysis conveniently.

A brominated flame retardant (BFR), hexabrominated heterocyclic tris-(2,3-dibromopropyl) isocyanurate (TBC), was identified,forthe first time, in the natural environment.The chemical was found in river water (2.33-163 ng/L), surface sediments (85.0 ng/g-6.03 microg/g dry weight (dw)), soils (19.6-672 ng/g dw), earthworm (9.75-78.8 ng/g dw), and carp samples (12.0-646 ng/g dw) from a factory-polluted area in southern China. It was found that TBC can strongly adsorb to organic material in sediment, and a trend of decreasing concentration with distance from the source in soil and earthworm samples, combined with calculated Kow (octanol-water partition coefficient) and Koa (octanol-air partition coefficient), suggests its potential ability to undergo regional transportation through dust deposition. Calculated results showed high Kow (log Kow = 7.37) and bioaccumulation factor (BAF) (log BAF = 4.30) of this BFR and indicate that TBC has semivolatile properties and bioaccumulation characteristic in certain biological species. Quantitative structure property relationships (QSPRs) modeling revealed that TBC has Koa (log Koa = 23.68) and Kaw (air-water partition coefficient) (log Kaw = -16.31) values several orders higher than those of other BFRs. The identification of this chemical additive further reminds us that the production and usage of heterocyclic BFRs may cause potential contamination to the surrounding environment

On the basis of non-aqueous capillary electrophoresis (NACE) and micellar electrokinetic chromatography (MEKC), a novel technique, non-aqueous micellar electrokinetic chromatography (NAMEKC), has been established. NAMEKC has the advantages of NACE and uses the separation mechanism of MEKC, showing special advantages for separation of hydrophobic compounds. Separation of three of the priority pollutants by U. S. Environmental Protection Agency (EPA), i. e. dimethyl phthalate (DMP), diethyl phthalate (DEP), and dibutyl phthalate (DBP), were realized in 15 min. Important factors on separation, such as the amount of water added in the electrophoretic running buffer, the acidity of water phase, the organic additive, and the concentration of sodium dodecyl sulfate (SDS), were investigated. The proportion of water in the electrophoretic running buffer could affect the current and the stability of SDS micelle. Organic additives and the acidity of water phase showed no effect on increasing resolution. The concentration of SDS was a dominant factor, affecting the partition of analytes in micelle. DMP, DEP, and DBP were separated in a short time under the optimized operation conditions using 20 mmol/L NaH2PO4 and 120 mmol/L SDS in formamide/water (9/1, v/v). The application of NAMEKC leads to successful separation of the three typical hydrophobic compounds, which provides a novel means to separate and analyze hydrophobic compounds.

Based on the "coffee-ring effect", we developed a highly efficient SERS platform which integrates the fabrication of SERS-active substrates and the preconcentration of analytes into one step. The high sensitivity, robustness, reproducibility and simplicity make this platform ideal for on-site analysis of small volume samples at low concentrations in complex matrices.

Volatile species generation-flameless/flame atomization-atomic fluorescence spectrometry (VSG-FL/FA-AFS) without chromatographic separation was developed for quantitative determination of inorganic mercury (IHg) and methylmercury (MeHg) in water and biological samples by using a commercially available atomic fluorescence spectrometer. In the proposed method, inorganic mercury was measured by using the flameless mode. However, by using the flame atomization mode, the volatile hydride of MeHg generated by KBH4 can be transformed to elemental mercury vapour in the reductive argon–hydrogen flame, and both MeHg and IHg give a fluorescence signal in this flame atomization mode. Then, the concentration of MeHg can be calculated by subtracting IHg concentration from the total mercury concentration. The limits of detection for IHg and MeHg were 0.03 μg L−1 and 0.05 μg L−1, respectively. Spiked environmental water samples including seawater, tap water and river water were determined and satisfactory recoveries were obtained for MeHg and IHg. Furthermore, the proposed method was successfully applied to analyze biological certified reference material, TORT-2 (lobster hepatopancreas).

Methylation is an important transformation process for elements in the environment. Herein, headspace solid phase micro-extraction (HP-SPME) coupled with gas chromatography–flame photometric detection (GC-FPD) or gas chromatography–mass spectrometry (GC–MS) techniques were employed to study the photochemical methylation of inorganic tin(II) by eight organic compounds (including acetone, pyruvic acid, acetic acid, propionic acid, dimethyl sulfoxide, N,N-dimethylformamide, tert-butyl alcohol and isopropyl alcohol) in aqueous solutions. The major products were identified as monomethyltin (MMT) and dimethyltin (DMT), as well as trimethyltin (TMT) as the minor product. The yields of methyltin products were closely related to the chemical structures of methyl donors, and the pH and salinity of the reaction solution. The concentrations of methyltin products peaked at a pH of 5.0 and a salinity of 0.5 M. The dominating product also changed from MMT to DMT with an increase in pH value. Notably, pyruvic acid can readily methylate tin(II) under irradiation by sunlight in view of its absorption of sunlight, demonstrating that photochemical methylation is a possible transformation pathway for tin(II) in the environment.

A novel method using capillary electrophoresis (CE) coupled with inductively coupled plasma mass spectrometry (ICP-MS) for the separation of four organotin compounds has been developed. Semi-permanent coating of dioctadecyl dimethyl ammonium chloride (DDAC) was applied and investigated to enhance separation efficiency of trimethyltin (TMT) chloride, tributyltin (TBT) chloride, dibutyltin (DBT) dichloride and monobutyltin (MBT) trichloride. The electrolyte composition and ionic strength were optimized. Running buffer containing 0.608 mol L−1 HAc and 7 mmol L−1 NaAc was selected for the separation. The detection limits of the four organotin compounds ranged from 0.037 to 0.112 mg L−1 (as Sn) and the values of the relative standard deviation (RSD) were below 3.1% for migration time, less than 7.8% for peak height and not more than 8.4% for peak area. The developed method was successfully applied for speciation analysis of four organotin compounds in one certified reference material (CRM 477, mussel tissue), and environmental samples including water samples, grape wine and biological samples (Mya arenaria Linnaeus). The determined values (as organotin compounds) of CRM 477 (1.81 ± 0.13 (TBT), 1.36 ± 0.16 (DBT), 1.17 ± 0.18 (MBT)) were in good agreement with the certified values (2.20 ± 0.19 (TBT), 1.54 ± 0.12 (DBT), 1.50 ± 0.28 (MBT)). 0.325 mg L−1 MBT and 1.02 μg g−1 (as Sn) TBT were found in grape wine and Mya arenaria Linnaeus samples.

By adding L-cysteine into the mobile phase of chromatography, a simple on-line high performance liquid chromatography-cold vapor generation-atomic fluorescence spectrometry (HPLC-CV-AFS) method for separation and determination of divalent mercury (Hg2+), monomethylmercury (MMC) and ethylmercury (EMC) was developed. Compared with the conventional HPLC-UV-CV-AFS hyphenated systems, the proposed HPLC-CV-AFS system is very simple and low cost as no strong oxidant, no additional post-column interface, such as ultraviolet or microwave, and no organic solvent were needed. Parameters influencing mercury separation and determination were optimized in detail. The detection limits for MMC, EMC and Hg2+, based on three folds of baseline noise and 100 μL injection, were 0.05, 0.07, and 0.1 μg L−1, respectively. The relative standard deviation (RSD) for three parallels determinations varied from 1.4 to 2.5% at a concentration level of 50 μg L−1. The proposed method was successfully applied to analyze two certified reference material, DORM-2 (dogfish muscle) and TORT-2 (lobster hepatopancreas), and biological samples.

Capable of preserving the sizes and shapes of nanomaterials during the phase transferring, Triton X-114 based cloud point extraction provides a general, simple, and cost-effective route for reversible concentration/separation or dispersion of various nanomaterials in the aqueous phase.

Association with Hg(2+) enhances the hydrophobicity and triggers the cloud point extraction of approximately 4 nm-diameter gold nanoparticle probes functionalized with mercaptopropionic acid and homocystine, which results in the color change of the TX-114-rich phase from colorless to red, and therefore provides a novel approach for visual and colorimetric detection of Hg(2+) with ultrahigh sensitivity and selectivity.

We propose an extraction methodology to extract toxic mercury species including methylmercury (MeHg) and ethylmercury (EtHg) in coal by comparing different extraction methods (shaking, ultrasonic and microwave assisted extraction) using different extraction solvents (TMA, KOH/CH3OH, HCl, and acidic CuSO4/KBr). Microwave assisted extraction at the power of 90 W for 5 min using TMA (tetramethylammonium hydroxide) as the extractant provided the highest and the most satisfactory extraction efficiency for MeHg and EtHg. Speciation analysis of mercury was done by HPLC-AFS. The obtained concentrations in a certified reference material (CRM-580) were in good agreement with the certificated values. Ten coal samples from China were analyzed using the proposed method. MeHg was detected in most of the samples (6 out of 10) and EtHg was detected only in one. The concentrations were at the sub-ng level. Other forms of organomercuries might be found in the samples. Considering the high toxicities of organomercuries and the huge amount of coal consumption every year, people should be made more aware.

Based on a novel photo-induced chemical vapour generation (CVG) with formic acid instead of the conventional K2S2O8/KBH4 system, an on-line coupled HPLC and atomic fluorescence spectrometry procedure was developed for the speciation of inorganic mercury, methylmercury (MeHg), ethylmercury (EtHg) and phenylmecury (PhHg). Under UV irradiation, the decomposition of organic mercury species and the reduction of Hg2+ could be completed in one step with this proposed photo-induced CVG system. The novel CVG system used formic acid only, which simplified the flow system and avoided the possibility of contamination originating from additional chemicals. A number of operating parameters including organic acid species, concentration of formic acid, pH, flow rate of formic acid and flow rate of carrier gas were optimized, and comparable method sensitivities with the conventional K2S2O8/KBH4 system were obtained. The limits of detection at the optimized conditions were 0.81, 0.20 and 0.87 μg L−1 for MeHg, EtHg and PhHg, respectively. The developed method was validated by determination of certified reference material DORM-2 and was further applied in determination of seafood samples. The new CVG system is simple, environmentally benign, and inexpensive for the speciation analysis of mercury. It is expected to have similar applications in other analytical atomic spectrometric techniques as well as speciation of other organic metal compounds.