Chromium removal from aqueous solutions using new silica gel conjugates of desferrioxamine or diethylenetriaminepentaacetic acid

Desferrioxamine (DFO) and diethylenetriaminepentaacetic acid (DTPA) conjugated with silica gel (IDFOSG and IDTPASG, respectively) were evaluated as adsorbents for chromium in aqueous solutions. Different parameters affecting adsorption such as pH, sorbent dosage, contact time, sample volume and potential of interfering ions have been optimized. The optimum pH for chromium binding was 4 for 100 mg of adsorbents at 5 min of table shaking with 5 mL sample volume of chromium solutions. Langmuir adsorption model described the removal of chromium ions. The adsorption capacity for chromium was 90% for IDFOSG and 83% for IDTPASG in single solutions, and at least 75% in multielemental solutions. Considering the removal efficacy, regeneration and stability, DFO-grafted silica gel was generally superior to its DTPA counterpart and may be applied to the removal of traces of chromium species from natural waters.

Ionogels at the Water-Energy Nexus for Desalination Powered by Ultralow-Grade Heat

Industrial processes emit enormous amounts of waste heat below 40 °C into the environment as it is cannot be used in other processes. Adsorption desalination can be driven by low-grade heat but has never been proven at temperatures below 40 °C as current adsorption materials require heat sources of 50-150 °C. Here, we present the first experimental study on adsorption desalination using a novel class of ionogel adsorption materials, which can be regenerated at 25 °C or a driving temperature difference of 5 °C. This outstanding property contrasts with the benchmarking silica gel, which requires heat sources of at least 50 °C. Ionogels are solid-state ionic materials retaining the sorption properties of the constituent ionic liquid. Thermodynamic vapor-liquid equilibrium data of water sorption on commercial ionic liquids reveal 1-ethyl-3-methylimidazolium acetate as the best fluid for this specific application. A full experimental characterization of the material is performed from imaging at the nanoscale to testing on a real adsorption desalinator. At 25 °C, the material achieves a specific daily water production of 6.7 kg_water/(kg_ionogel d), increasing to 17.5 kg_water/(kg_ionogeld) at 45 °C, outperforming silica gel by a factor of 2.

The HR-CS-GF-AAS determination and preconcentration of palladium in contaminated urban areas, especially in lichens

The increasing content of platinum group metal particles emitted into the environment by car traffic is gradually attracting the attention of the scientific community. However, the methods for the determination of platinum group metals in environmental matrices are either costly or suffer from low sensitivity. To facilitate the use of less sensitive, but significantly cheaper, devices, the preconcentration of platinum group metals is employed. For platinum, a multitude of preconcentration approaches have been published. On the contrary, the preconcentration approaches for palladium are still rare. In this work, the development, optimization, and testing of a new approach is described; it is based on a preconcentration of palladium on octadecyl modified silica gel together with the complexing agent dimethylglyoxime, and it is then analyzed with the high-resolution continuum-source atomic absorption spectrometry. For comparison, a newly developed sorbent, QuadraSil™ TA, with a high affinity for platinum group metals was also tested. The preconcentraiton approach was tested on the lichen Hypogymnia physodes, which served as a bioindicator of palladium emissions. The case study site was a mid-sized city in central Europe: Brno, Czech Republic. The dry "bag" monitoring technique was used to collect the palladium near roads with a large span of traffic density. The developed analytical approach confirmed an increasing concentration of palladium with increasing exposure time and intensity of the traffic. Consequently, a simple relationship between the amount of bioaccumulated palladium and traffic density was established.

Enhanced reductive dechlorination of trichloroethene with immobilized Clostridium butyricum in silica gel

Deteriorated environmental conditions during the bioremediation of trichloroethene (TCE)-polluted groundwater cause decreased treatment efficiencies. This study assessed the effect of applying immobilized Clostridium butyricum (a hydrogen-producing bacterium) in silica gel on enhancing the reductive dechlorination efficiency of TCE with the slow polycolloid-releasing substrate (SPRS) supplement in groundwater. The responses of microbial communities with the immobilized system (immobilized Clostridium butyricum and SPRS amendments) were also characterized by the metagenomics assay. A complete TCE removal in microcosms was obtained within 30 days with the application of this immobilized system via reductive dechlorination processes. An increase in the population of Dehalococcoides spp. was observed using the quantitative polymerase chain reaction (qPCR) analysis. Results of metagenomics assay reveal that the microbial communities in the immobilized system were distinct from those in systems with SPRS only. Bacterial communities associated with TCE biodegradation also increased in microcosms treated with the immobilized system. The immobilized system shows a great potential to promote the TCE dechlorination efficiency, and the metagenomics-based approach provides detailed insights into dechlorinating microbial community dynamics. The results would be helpful in designing an in situ immobilized system to enhance the bioremediation efficiency of TCE-contaminated groundwater.

The role of Trichoderma spp. and silica gel in plant defence mechanisms and insect response in vineyard

Several elicitors, stimulating induced resistance mechanisms, have potential in preventing or mitigating pathogen infections. Some of these compounds, triggering the production of jasmonic acid (JA), a precursor of herbivore-induced plant volatiles, could also play a central role in indirect resistance to pest species, by improving beneficial arthropod performance, and necrotrophic pathogens. In the current work, Trichoderma gamsii/T. asperellum and silica gel treatments - alone and in combination - were studied to evaluate the plant defence mechanism on grapevines (Vitis vinifera L.) by laboratory and field trials. JA production level was measured before and after Plasmopara viticola infection on potted vines. JA production induced by silica gel was higher than that caused by Trichoderma before infection. In Trichoderma-treated plants, JA production increased after P. viticola inoculation. In vineyard field trials, Mymaridae (Hymenoptera: Chalcidoidea) showed higher captures in transparent sticky traps on silica gel-treated plants, in comparison with control. On the other hand, no significant attraction was detected for Ichneumonoidea and other Chalcidoidea in silica gel and T. gamsii/T. asperellum-treated plants. The potential effects of elicitors are discussed, in the frame of attract and reward strategy.

Vegetal fiber paper matrix impregnated with silica gel for benzene removal

Removing benzene from indoor space plays an important role in indoor air purification. A novel filter with vegetal fiber paper (VFP) as matrix hosting silica gel is proposed in this paper for benzene removal. In order to investigate the feasibility and performance of this idea, firstly, three pieces of VFP samples impregnated with different amounts of silica gel are fabricated and their benzene adsorption quantities are tested. The results show that three times is recommended as the optimal number for impregnating. The VFP sample impregnated with silica gel after the third impregnating exhibits commendable coating stability and good benzene adsorption performance. Additionally, at low relative pressure (P_b /P_s  ≤ 0.05), the experimental data of benzene adsorption isotherms fit well with the Langmuir model with R² greater than 0.97. Then, two actual filters made of VFP impregnated with silica gel after the third impregnating were fabricated. It is found that the pressure drop of the actual filter is only 1200 Pa/m when the air velocity is 2 m/s. Besides, the one-pass efficiency of the filter can reach to 19.44%. It is expected that the silica gel coated on the filter can be modified to improve the purification performance of the filter.

A bioinspired hydrogen bond-triggered ultrasensitive ionic mechanoreceptor skin

Biological cellular structures have inspired many scientific disciplines to design synthetic structures that can mimic their functions. Here, we closely emulate biological cellular structures in a rationally designed synthetic multicellular hybrid ion pump, composed of hydrogen-bonded [EMIM+][TFSI-] ion pairs on the surface of silica microstructures (artificial mechanoreceptor cells) embedded into thermoplastic polyurethane elastomeric matrix (artificial extracellular matrix), to fabricate ionic mechanoreceptor skins. Ionic mechanoreceptors engage in hydrogen bond-triggered reversible pumping of ions under external stimulus. Our ionic mechanoreceptor skin is ultrasensitive (48.1-5.77 kPa-1) over a wide spectrum of pressures (0-135 kPa) at an ultra-low voltage (1 mV) and demonstrates the ability to surpass pressure-sensing capabilities of various natural skin mechanoreceptors (i.e., Merkel cells, Meissner's corpuscles, Pacinian corpuscles). We demonstrate a wearable drone microcontroller by integrating our ionic skin sensor array and flexible printed circuit board, which can control directions and speed simultaneously and selectively in aerial drone flight.

Optimization of Sample Pretreatment based on Graphene Oxide Dispersed Acid Silica Gel for Determination of Polybrominated Diphenyl Ethers in Vegetables near an E-waste Recycling Plant

Polybrominated diphenyl ethers (PBDEs) derived from e-waste dismantling, tend to easily bioaccumulate in vegetables. In this study, an optimized sample pretreatment method based on graphene oxide (GO) dispersed acid silica gel was used to determine PBDEs levels in vegetables. The recovery efficiency of the optimized method ranged between 90.3%-107.5% with the detection limit (LOD) being within 0.17-1.8 ng g^-1. Vegetable samples were grown nearby an e-waste recycling plant in Nanjing, China, and analyzed using the optimized method. The concentrations of ΣPBDEs in the samples ranged from 12.1 to 20.1 ng g^-1. This study developed an optimized sample pretreatment method to determine PBDEs in vegetables nearby e-waste contaminated sites and provides insights on the potential risks derived from e-waste dismantling to the surrounding environment.

Lethal Effects of Silica Gel-Based CimeXa and Kaolin-Based Surround Dusts Against Ixodid (Acari: Ixodidae) Eggs, Larvae, and Nymphs

As tick resistance to conventional acaricides becomes more common, alternative control tactics are gaining attention. Insecticidal dusts CimeXa and Surround, based on silica gel and kaolin, respectively, were assessed against Amblyomma americanum (L.) (Ixodida: Ixodidae) eggs, larvae, and nymphs in the laboratory. Coverage by the dry dusts, particularly CimeXa, was strongly lethal to larvae and to a lesser extent to nymphs. Larval mortality was also high when larvae crawled across thin layers of CimeXa and, to a lesser extent, Surround dusts. CimeXa was more lethal to nymphs that crawled across a thin layer than Surround. Larval mortality after crawling on dried aqueous suspensions of the dusts for 30 min and for 48 h caused moderate mortality (<80%) regardless of a 10-fold difference in concentration; nymphal mortality was negligible. In a field experiment, CimeXa dust strongly reduced numbers of Gulf coast tick, Amblyomma maculatum (Koch) (Ixodida: Ixodidae), larvae and nymphs by 24 h. Possible application of CimeXa to control other species of ixodid ticks is discussed as well as advantages and disadvantages of using dusts for tick control under field conditions.

Enantioselective resolution of 2-arylpropionic acid derivatives employing immobilization of lipase from Bacillus subtilis strain Kakrayal_1 (BSK-L)

This work studied the enantioselective resolution of 2-arylpropionic acid derivatives employing immobilization of lipase produced by Bacillus subtilis strain Kakrayal_1 (BSK-L). The efficient immobilization of lipase on modified silica gel was confirmed by Fourier transform infrared spectroscopy. Tethering of lipase facilitated the enhancement of physiochemical properties and stability of enzyme. Covalently immobilized enzyme retained 85% of residual activity even on reuse after 10th reaction cycle. Validation of immobilized lipase for enantioselective resolution of 2-arylpropionic acid derivatives led to 47.8% conversion efficiency with 87% enantiomeric excess (ee) for ketoprofen, and 27.3% conversion efficiency with 75% ee for flurbiprofen. The enantioselective resolution using immobilized lipase (BSK-L) was superior to free and commercially procured lipase, which suggest a potential application of immobilized lipase in the pharmaceutical/chemical industry.

Trace Level Analysis of Sarin and VX in Food Using Normal Phase Silica Gel and Ultra-Performance Liquid Chromatography-Time-of-Flight Mass Spectrometry (UPLC-TOF-MS)

Ultra-Performance Liquid Chromatography/electrospray ionization mass spectrometry was used for the trace level determination of isopropyl methylphosphonofluoridate (Sarin, GB) and ( O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) after extraction from various foods. A method utilizing normal phase silica gel was developed for the sample preparation and extraction of VX and GB from food. The extraction efficiencies of the normal phase silica gel method for VX was compared to those of other commercial solid phase extraction media and was found to be comparable. Sarin was found to be incompatible with both the mixed mode cation exchange (MCX) sorbents and QuEChERS methods that are commercially available but was successful with the normal phase silica gel method. The linear range of quantitation for VX was 0.1-330 ng/mL and for GB was 20-1200 ng/mL. The average recoveries of VX and GB from the various food matrices along with the corresponding relative standard deviations (RSDs) are reported.

Hydroxyl Radical Based Photocatalytic Degradation of Halogenated Organic Contaminants and Paraffin on Silica Gel

Photochemical materials are of scientific and practical importance in the field of photocatalysis. In this study, the photochemistry of several organic contaminants, including decabromodiphenyl ether (BDE-209), halogenated phenols (C₆ X₅OH, X = F, Cl, Br) and paraffin, on silica gel (SG) surface was investigated under simulated solar irradiation conditions. Photolysis of these compounds at the solid/air interface proceeds with different rates yielding various hydroxylation products, and hydroxyl radical was determined as the major reactive species. According to density functional theory (DFT) calculations, the reaction of physically adsorbed water with reactive silanone sites (>Si═O) on silica was indispensable for the generation of ^•OH radical, where the required energy matches well with the irradiation energy of visible light. Then, the BDE-209 was selected as a representative compound to evaluate the photocatalytic performance of SG under different conditions. The SG material showed good stability in the photodegradation process, and was able to effectively eliminate BDE-209 under natural sunlight. These findings provide new insights into the potential application of SG as a solid surface photocatalyst for contaminants removal.

Soluble and Nanoporous Silica Gel-Entrapped C. freundii Methionine γ-Lyase

Methionine γ-lyase is a pyridoxal 5'-phosphate dependent tetramer that catalyzes the α,γ-elimination of methionine in ammonia, methanethiol and α-ketobutyrate. MGL catalytic power has been exploited as a therapeutic strategy to reduce the viability of cancer cells or bacteria. In order to obtain a stable enzyme to be delivered at the site of action, MGL can be encapsulated in a variety of matrices. As a reference encapsulation strategy we have prepared MGL nanoporous wet silica gels. Immobilized MGL gels were characterized with regards to activity, stability, absorption, circular dichroism and fluorescence properties and compared with soluble MGL. We found that MGL gels exhibit (i) spectroscopic properties very similar to MGL in solution, (ii) a higher stability with respect to the soluble enzyme and (iii) catalytic activity six-fold lower than in solution. These findings prove that MGL encapsulation is a suitable strategy for therapeutic applications.

Silica immobilization of Geobacter sulfurreducens for constructing ready-to-use artificial bioelectrodes

Microbial electrochemical technologies (METs) rely on the control of interactions between microorganisms and electronic devices, enabling to transform chemical energy into electricity. We report a new approach to construct ready-to-use artificial bioelectrodes by immobilizing Geobacter sulfurreducens cells in composite materials associating silica gel and carbon felt fibres. Viability test confirmed that the majority of bacteria (ca. 70 ± 5%) survived the encapsulation process in silica and that cell density did not increase in 96 h. The double entrapment within the silica-carbon composite prevented bacterial release from the electrode but allowed a suitable mass transport (ca. 5 min after electron donor pulse), making the electrochemical characterization of the system possible. The artificial bioelectrodes were evaluated in three-electrode reactors and the maximum current displayed was ca. 220 and 150 μA cm-3 using acetate and lactate as electron donors respectively. Cyclic voltammetry of acetate-fed bioelectrodes revealed a sigmoidal catalytic oxidation wave, typical of more advanced-stage biofilms. The presence of G. sulfurreducens within composites was ascertained by SEM analysis, suggesting that only part of the bacterial population was in direct contact with the carbon fibres. Preliminary analyses of the transcriptomic response of immobilized G. sulfurreducens enlightened that encapsulation mainly induces an osmotic stress to the cells. Therefore, ready-to-use artificial bioelectrodes represent a versatile time- and cost-saving strategy for microbial electrochemical systems.

Novel thin-layer chromatographic method of screening the anthocyanes containing alimentary products and precautions taken at the method development step

The purpose of this study was to develop a novel and cost-effective thin-layer chromatographic method (TLC) using cellulose powder as stationary phase for authentication of the selected fruit-based alimentary products and targeting anthocyanes as the authenticity markers. Our method outperformed the HPTLC method earlier developed by another research team using silica gel as stationary phase. It was demonstrated that due to a limited chemical stability of anthocyanes, employing them as authenticity markers is burdened with a non-negligible uncertainty risk. Hydrolytic split of the glycosides into the aglycone and carbohydrate moieties can lead to a confusing multiplication of chromatographic bands and therefore it is advisable to use for the authentication purposes a limited set of well selected and stable enough anthocyane markers. Cyanin chloride, keracyanin chloride, pelargonidin chloride and delphinidin chloride were selected as the external standards and for the development of the calibration curves. The TLC-obtained LOD and LOQ values were 0.025 and 0.075μgspot^-1 for cyanin, 0.055 and 0.166μgspot^-1 for keracyanin, 0.047 and 0.140μgspot^-1 for pelargonidin, and 0.171 and 0.513μgspot^-1 for delphinidin, respectively. The analogous HPTLC-obtained LOD and LOQ values were 0.107 and 0.321μgspot^-1 for cyanin, 0.189 and 0.566μgspot^-1 for keracyanin, and 0.161 and 0.484μgspot^-1 for pelargonidin, respectively. Delphinidin was not detectable with use of the HPTLC method. Consequently, quantification of anthocyanes in the alimentary products carried out with use of TLC allowed identification of more target compounds and in a higher number of alimentary products than it was possible with use of HPTLC, apparently due to the LOD levels by one magnitude order lower for TLC than HPTLC.

Pullulan microbeads/Si-HPMC hydrogel injectable system for the sustained delivery of GDF-5 and TGF-β1: new insight into intervertebral disc regenerative medicine

Discogenic low back pain is considered a major health concern and no etiological treatments are today available to tackle this disease. To clinically address this issue at early stages, there is a rising interest in the stimulation of local cells by in situ injection of growth factors targeting intervertebral disc (IVD) degenerative process. Despite encouraging safety and tolerability results in clinic, growth factors efficacy may be further improved. To this end, the use of a delivery system allowing a sustained release, while protecting growth factors from degradation appears of particular interest. We propose herein the design of a new injectable biphasic system, based on the association of pullulan microbeads (PMBs) into a cellulose-based hydrogel (Si-HPMC), for the TGF-β1 and GDF-5 growth factors sustained delivery. We present for the first time the design and mechanical characterization of both the PMBs and the called biphasic system (PMBs/Si-HPMC). Their loading and release capacities were also studied and we were able to demonstrate a sustained release of both growth factors, for up to 28 days. Noteworthy, the growth factors biological activity on human cells was maintained. Altogether, these data suggest that this PMBs/Si-HPMC biphasic system may be a promising candidate for the development of an innovative bioactive delivery system for IVD regenerative medicine.

Adsorption and Biodegradation of Aromatic Chemicals by Bacteria Encapsulated in a Hydrophobic Silica Gel

An adsorbent silica biogel material was developed via silica gel encapsulation of Pseudomonas sp. NCIB 9816-4, a bacterium that degrades a broad spectrum of aromatic pollutants. The adsorbent matrix was synthesized using silica precursors methyltrimethoxysilane and tetramethoxysilane to maximize the adsorption capacity of the matrix while maintaining a highly networked and porous microstructure. The encapsulated bacteria enhanced the removal rate and capacity of the matrix for an aromatic chemical mixture. Repeated use of the material over four cycles was conducted to demonstrate that the removal capacity could be maintained with combined adsorption and biodegradation. The silica biogel can thus be used extensively without the need for disposal, as a result of continuous biodegradation by the encapsulated bacteria. However, an inverse trend was observed with the ratio of biodegradation to adsorption as a function of log K_ow, suggesting increasing mass-transport limitation for the most hydrophobic chemicals used (log K_ow > 4).

High performance thin-layer chromatography-mass spectrometry of Japanese knotweed flavan-3-ols and proanthocyanidins on silica gel plates

On-line elution based TLC-MS is now a well-established technique, but the quality of the data obtained can sometimes be hampered by a severe spectral background or by strong ion suppression, especially when silica gel plates are used in combination with an acidic modifier in the developing solvent. We solved this issue simply and efficiently using two pre-developments of the plates, firstly with methanol-formic acid (10:1, v/v) and secondly with acetonitrile-methanol (2:1, v/v). This solution resulted in significant improvement in the sensitivity of HPTLC-MS methods. The applicability of this approach was proven on analysis of flavan-3-ols and proanthocyanidins in crude extracts of Japanese knotweed (Fallopia japonica Houtt.) rhizomes. Separations on HPTLC silica gel and HPTLC silica gel MS grade plates using developing solvents toluene-acetone-formic acid (3:3:1, 6:6:1, 3:6:1, v/v) and dichloromethane-acetone-formic acid (1:1:0.1, v/v) were followed by post-chromatographic derivatization with 4-dimethylaminocinnamaldehyde (DMACA) detection reagent. Examination of the stability of the analytes on the start confirmed that the plates should be developed immediately after the application of standards and sample test solutions. In a five hours stability testing after development we discovered an unexpected phenomenon of enhanced absorption at 280nm. However, based on an experiment with post-chromatographic derivatization with DMACA detection reagent, the analytes were proven to be sufficiently stable in the time frame of an HPTLC-MS analysis. This was important for development of the first HPTLC-MS and HPTLC-MSⁿ methods for identification of flavan-3-ols and B-type proanthocyanidins from monomers up to decamers. For the first time, based on this research methodology, trimers, trimer gallates, tetramer gallates, pentamers, pentamer gallates, hexamers, hexamer gallates, heptamers, octamers, nonamers and decamers were tentatively identified in Japanese knotweed rhizomes. Additionally, all developed HPTLC-MS methods have enabled simultaneous identification of stilbenes (resveratrol, piceatannol hexoside, piceid) and anthraquinones (emodin, emodin-O-hexoside, emodin-O-(acetyl)-hexoside and emodin-O-(6'-O-malonyl)-hexoside).

HPLC Separation of Diastereomers: Chiral Molecular Tools Useful for the Preparation of Enantiopure Compounds and Simultaneous Determination of Their Absolute Configurations

To obtain enantiopure compounds, the so-called chiral high performance liquid chromatography (HPLC) method, i.e., HPLC using a chiral stationary phase, is very useful, as reviewed in the present Special Issue. On the other hand, normal HPLC (on silica gel) separation of diastereomers is also useful for the preparation of enantiopure compounds and also for the simultaneous determination of their absolute configurations (ACs). The author and coworkers have developed some chiral molecular tools, e.g., camphorsultam dichlorophthalic acid (CSDP acid), 2-methoxy-2-(1-naphthyl)propionic acid (MαNP acid), and others suitable for this purpose. For example, a racemic alcohol is esterified with (S)-(+)-MαNP acid, yielding diastereomeric esters, which are easily separable by HPLC on silica gel. The ACs of the obtained enantiopure MαNP esters can be determined by the ¹H-NMR diamagnetic anisotropy method. In addition, MαNP or CSDP esters have a high probability of giving single crystals suitable for X-ray crystallography. From the X-ray Oak Ridge thermal ellipsoid plot (ORTEP) drawing, the AC of the alcohol part can be unambiguously determined because the AC of the acid part is already known. The hydrolysis of MαNP or CSDP esters yields enantiopure alcohols with the established ACs. The mechanism and application examples of these methods are explained.

In situ speciation of dissolved inorganic antimony in surface waters and sediment porewaters: development of a thiol-based diffusive gradients in thin films technique for Sb(III)

Antimony is a priority environmental contaminant typically present as either the trivalent (Sb(III)) or the pentavalent (Sb(V)) oxidation state in aquatic systems. Both the toxicity and mobility of antimony are affected by its speciation, and thus the accurate measurement of antimony speciation is essential for investigating the behaviour of this contaminant in aquatic systems. Here we present a diffusive gradients in thin films (DGT) technique, which utilises a binding layer containing a thiol-based adsorbent (3-mercaptopropyl functionalised silica gel), for the selective measurement of Sb(III) in surface waters and sediment porewaters. We also evaluated the Metsorb DGT technique, which has been previously reported to accurately measure Sb(V), for its ability to accumulate Sb(III) and thus allow the measurement of total inorganic antimony. Both the mercapto-silica and Metsorb DGT techniques showed a high affinity for Sb(III), with uptake efficiencies >97%. Elution efficiencies of 86.9 ± 2.6% and 88.1 ± 1.2% were obtained for mercapto-silica and Metsorb, respectively, with 1 mol L(-1) H2O2 in 1 mol L(-1) NaOH. The accumulation of Sb(III) by these DGT techniques was linear with time (R(2) > 0.99) and unaffected by pH (4.07-8.05), ionic strength (0.001-1.0 mol L(-1) NaCl), bicarbonate (1-15 mmol L(-1)), and an artificial seawater matrix (pH 8.34; salinity 34.8). Finally, the mercapto-silica DGT technique was applied to measure porewater concentrations of Sb(III) and As(III) in a contaminated freshwater sediment at high resolution.

Simple and fast colorimetric detection of inorganic arsenic selectively adsorbed onto ferrihydrite-coated silica gel using silver nanoplates

The optical detection for inorganic arsenic (As) semi-quantitative determination is presented by using silver nanoplates (AgNPls). The color of AgNPs is immediately changed in the presence of As(III) and As(V) with the same sensitivity. To improve the selectivity of AgNPls for As detection, ferrihydrite-coated silica gel (SiO2-Fh) was specifically exploited as adsorbent for arsenic prior to As detection by AgNPls. The developed method provides the detection limit of 0.5ppm with the detection range between 0.5ppm and 30.0ppm for As determination observed with naked eye, and allows to determine total inorganic arsenic. This is the first report of As detection approach combining As removal technology together with nanotechnology. This combined technique provides a rapid, sensitive and selective method for monitoring As levels in aqueous samples, and can be employed as a testing field kit to screen arsenic contamination outside of a laboratory.

Engineering of a silica encapsulation platform for hydrocarbon degradation using Pseudomonas sp. NCIB 9816-4

Industrial application of encapsulated bacteria for biodegradation of hydrocarbons in water requires mechanically stable materials. A silica gel encapsulation method was optimized for Pseudomonas sp. NCIB 9816-4, a bacterium that degrades more than 100 aromatic hydrocarbons. The design process focused on three aspects: (i) mechanical property enhancement; (ii) gel cytocompatibility; and (iii) reduction of the diffusion barrier in the gel. Mechanical testing indicated that the compressive strength at failure (σf ) and elastic modulus (E) changed linearly with the amount of silicon alkoxide used in the gel composition. Measurement of naphthalene biodegradation by encapsulated cells indicated that the gel maintained cytocompatibility at lower levels of alkoxide. However, significant loss in activity was observed due to methanol formation during hydrolysis at high alkoxide concentrations, as measured by FTIR spectroscopy. The silica gel with the highest amount of alkoxide (without toxicity from methanol) had a biodegradation rate of 285 ± 42 nmol/L-s, σf  = 652 ± 88 kPa, and E = 15.8 ± 2.0 MPa. Biodegradation was sustained for 1 month before it dropped below 20% of the initial rate. In order to improve the diffusion through the gel, polyvinyl alcohol (PVA) was used as a porogen and resulted in a 48 ± 19% enhancement in biodegradation, but it impacted the mechanical properties negatively. This is the first report studying how the silica composition affects biodegradation of naphthalene by Pseudomonas sp. NCIB 9816-4 and establishes a foundation for future studies of aromatic hydrocarbon biodegradation for industrial application.

Recyclable Bifunctional Polystyrene and Silica Gel-Supported Organocatalyst for the Coupling of CO2 with Epoxides

A bifunctional ammonium salt covalently bound to a polystyrene or silica support proved to be an efficient and recyclable catalyst for the solvent-free synthesis of cyclic carbonates from epoxides and CO2 . The catalyst can be easily recovered by simple filtration after the reaction and reused in up to 13 consecutive runs with retention of high activity and selectivity even at 90 °C. The scope and limitations of the reaction has been evaluated in terms of reaction conditions and substrate scope.

[Chemical constituents from Artemisia annua]

OBJECTIVE

To investigate the chemical constituents of dried whole plants of Artemisia annua.

METHOD

The chemical constituents were isolated by repeated silica gel chromatography, medium pressure column chromatography, and semi-preparative HPLC, and their structures were elucidated by spectroscopic analyses and comparison of NMR data with those reported in literature.

RESULT

15 compounds were isolated and identified to be 5-O-[(E)-Caffeoyl] quinic acid(l), 1,3-di-O-caffeoylquinic acid(2), 4 5-di-O-caffeoylquinic acid(3), 3, 5-di-O-caffeoylquinic acid (4), 3, 4-di-O-caffeoylquinic acid (5), methyl-3,4-di-O-caffeoylquinic acid(6), methyl-3,5-di-O-caffeoylquinic acid(7), 3,6'-O-diferuloylsucrose(8), 5'-β-D-glucopyranosyloxyjasmonic acid(9), Scopoletin(10), scoparone (11), 4-O-β-D-glucopyranosyl-2-hydroxyl-6-methoxyacetophenone (12), chrysosplenol D (13), casticin (14), chrysosplenetin(15).

CONCLUSION

Compounds 2, 6, 8 and 9 are obtained from the Artemisia genus for the first time. Compounds 7 and 15 are obtained from this plant for the first time.

[Chemical constituents of flavonoids and their glycosides in Melastoma dodecandrum]

The chemical constituents of 95% ethanol extract of Melastoma dodecandrum were isolated and purified by chromatography on silica gel, Sephadex LH-20, and HPLC, to obtain thirteen compounds eventually. On the basis of their physico-chemical properties and spectroscopic data, these compounds were identified as quercetin (1), quercetin-3-O-β-D-glucopyranoside (2), quercetin-3-O-(6"-O-p-coumaroyl) -β-D-glucopyranoside (3), kaempferol (4), kaempferol-3-O-β-D-glucopyranoside (5), kaempferol-3-O- [2",6"-di-O-(E)-coumaroyl]-β-D-glucopyra-noside (6), luteolin (7), luteolin-7-O-(6"-p-coumaroyl) -β-D-glucopyranoside (8), apigenin (9), apigenin-7-(6"-acetyl-glucopyranoside) (10) , naringenin (11), isovitexin (12), and epicatechin-[8,7-e] -4β-(4-hydroxyphenyl)-3,4-dyhydroxyl-2(3H)-pyranone (13). Eight compounds(3,5,6,8-11 and 13) were obtained from M. dodecandrum for the first time.