Trace Compounds Research Articles

Evaluation of the Wheeler-Jonas parameters for biogas trace compounds removal with activated carbons

A practical and feasible solution to reduce the global impacts from fossil fuels is represented by the locally distributed micro-cogeneration systems with high temperature solid oxide fuel cells (SOFC) fed by biogenous fuel coupled in an energy distributed system. One of the main drawback is the low tolerability towards certain fuel impurities, mostly sulfur, chlorine and siloxane compounds. The opportunity to predict the breakthrough time of a gas cleaning section with a high precision level is mandatory to meet SOFC requirements. The reaction kinetic equation called the Wheeler-Jonas equation is adopted to estimate this breakthrough time. Two different commercial activated carbons were studied estimating the breakthrough time varying the operating temperature, the pollutant concentration (single and multiple effects) and the relative humidity. Results showed how relative humidity content affects inversely the removal performance for both sorbents. The Carbox sample, below RH 20% showed interesting results due to its metals content and microstructure. Here, relative humidity promoted the best condition to remove organic vapors from the biogas stream. Multiple contaminant conditions for both sorbent materials decreased the removal performance (tb). This decreasing for the Carbox sample ranged from a minimum of 44% to a maximum of 50% for H2S, and 70% for HCl with wet and dry conditions respectively.

Analysis of crude oils using gas purge microsyringe extraction coupled to comprehensive two dimensional gas chromatography-time-of-flight mass spectrometry

As a complex mixture, the analysis of individual compounds in crude oil is a great challenge. The traditional sample preparation method such as column chromatography is time-consuming, solvent-wasting, and very possible to cause the loss of light hydrocarbons. In addition, coelution of compounds with similar boiling points or polarities often occurs in one dimensional gas chromatography–mass spectrometry (1D GC–MS). To overcome these disadvantages, a homemade gas purge microsyringe extraction (GP-MSE) device was prepared and coupled to comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) for the analysis of crude oils from different regions. The extraction conditions of GP-MSE were optimized in detail. The whole process of GP-MSE extraction only takes 7min, only 20μL of organic solvent is needed, and almost complete extraction of analytes is achieved. Compared with the common used methods, light hydrocarbons in all the samples were well retained and more compounds were separated and identified, including diamondoid series, pyrrolic nitrogen compounds and other important biomarkers such as terpane and sterane series. Coelution of compounds in 1D GC–MS was eliminated in GC×GC-TOFMS. Based on the developed GP-MSE-GC×GC-TOFMS, the distribution of trace compounds in crude oils and effect of biodegradation were discussed in detail.

Triclosan restructures gut communities

Toxicology![Figure][1] Ingesting organic compounds can modify the gut microbial communities in zebrafish. PHOTO: KAZAKOV MAKSIM/SHUTTERSTOCK Trace organic compounds can have a range of unintended consequences for environmental ecosystems and exposed animals. The adverse health effects of the antimicrobial compound triclosan and its degradation by-products, for example, have led to bans of its use in some consumer products. Gaulke et al. show how triclosan modifies gut microbial communities after ingestion. In zebrafish fed triclosan-laced diets, gut community composition dramatically shifted over short time intervals. Some community members were highly susceptible to triclosan exposure, whereas others, including members of the genus Pseudomonas and the family Rhodobacteraceae, were more resistant. Overall, triclosan exposure altered ecological dynamics and interaction networks, demonstrating how such trace compounds can have a profound impact on the gut microbiome. PLOS ONE 10.1371/journal.pone.0154632 (2016). [1]: pending:yes

Preparation of amino acid-based polymer functionalized magnetic nanoparticles as adsorbents for analysis of plant growth regulators in bean sprouts

A novel magnetic solid phase extraction (MSPE) adsorbent has been developed for enriching two plant growth regulators, including 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chlorophenoxyacetic acid (4-CPA), in bean sprouts. For preparing the MSPE adsorbent, poly(N-methacryloyl-L-phenylalanine methyl ester (P(MA-L-Phe-OMe)), amino acid-based polymer, was modified onto the magnetic nanoparticles via “grafting to” method by free radical polymerization. The resultant P(MA-L-Phe-OMe)-functionalized magnetic nanoparticles (Fe3O4@P(MA-L-Phe-OMe)) were characterized by Fourier transform infrared (FT-IR) spectroscopy and elemental analysis. The adsorption amount of Fe3O4@P(MA-L-Phe-OMe) nanoparticles to 2,4-D and 4-CPA were 39.82mgg−1 and 29.02mgg−1, respectively. Moreover, the prepared MSPE adsorbents showed good selectivity towards 2,4-D and 4-CPA due to the hydrophobic interactions and electrostatic forces between the target analytes and Fe3O4@P(MA-L-Phe-OMe). The results demonstrated that the proposed MSPE adsorbents have high affinity to the targets 2,4-D and 4-CPA. Under the optimized conditions, the proposed materials were successfully applied to enrich 2,4-D and 4-CPA in bean sprouts samples. The recovery values of the bean sprouts solution spiked the targets were from 90.9% to 96.4% with the relative standard deviations of 2.3–3.9%. Our work proved that the novel Fe3O4@P(MA-L-Phe-OMe) nanoparticles were the good adsorbents of magnetic solid phase extraction (MSPE) and have good potential for the analysis of trace compound in real samples.

Microstructure-Enhanced Liquid–Liquid Extraction in a Real-Time Fluorescence Detection Microfluidic Chip

Microfluidic system is widely employed in the detection of environmental contaminants and biological specimens. One of the critical issues which limits the applications of microfluidic chips is the limit of detection of trace specimens. Liquid–liquid extraction is of great importance in the preprocessing in microfluidic devices. In this paper, we developed a real-time fluorescence detection microfluidic chip combined with a microstructure-enhanced liquid–liquid laminar extraction technique, which concentrated the trace compound and realized real-time monitoring. Auxiliary microstructures integrated in the microfluidic chip were applied to increase the extraction efficiency, which was proved by the FEM (finite element method) simulation as well. A common fluorescence probe, Rhodamine 6G (Rh6g), was used in the experiment to demonstrate the performance of the microfluidic system. It revealed that the liquid–liquid laminar extraction combined with auxiliary microstructures of a cross shape was an effective method for enrichment. The efficiency of microstructure-enhanced liquid–liquid extraction was increased by 350% compared to the traditional laminar flow extraction.

Biogas trace compound removal with ashes using proton transfer reaction time-of-flight mass spectrometry as innovative detection tool

The feasibility of reusing waste materials as an inexpensive sorbent to remove volatile organic compounds from gaseous waste streams has been demonstrated. Ashes from wood-chips were tested as sorbent materials for VOCs removal with a PTR-ToF-MS instrument. Both scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) and BET analysis were used to identify the structural characteristics, elemental composition and surface area of the tested ashes respectively.Most of the tentatively identified compounds were less strongly adsorbed by wet ash: thiols, siloxanes, carbonyl compounds and terpenes. Hydrogen sulfide and alcohols show improving removal performance in wet conditions. These results are related to the water solubility properties. Siloxanes were tentatively identified and monitored with PTR-ToF-MS. This demonstrates how this instrument is a suitable tool for simultaneously providing a multitude of analysis for rapid in situ monitoring of fuel contaminants.Considering the low cost, and the recycling of environmental pollutants, wood ashes are a possible choice for VOCs removal from biogas.

Screening of minor bioactive compounds from herbal medicines by in silico docking and the trace peak exposure methods

Screening of high potent enzyme inhibitors from herbal medicines is always lacking of efficiency due to the complexity of chemicals. The constituents responsible for the holistic effect may be trace-level chemicals, but these chemicals were covered by highly abundant compositions. To challenge this bottleneck, a strategy for screening minor bioactive compounds was proposed. It generally included four steps, (1) preliminarily find the enzyme binders by ultrafiltration; (2) optimise and predict the potential inhibitors by docking analysis; (3) selectively identify and prepare trace compounds by segment and exposure approach; (4) validate the activity and summarize the structure-activity relationship. As a case study, α-glucosidase (AGH) and Ginkgo biloba extract were used as the experimental materials. By comprehensive screening, 11 trace flavones were screened out and identified as strong AGH inhibitors. Among them, AGH inhibitory activities of syringetin and sciadopitysin were reported for the first time. Their IC50 values were 36.80 and 8.29μM, respectively, which were lower than that of a positive control acarbose. In addition, the AGH inhibitory activities of the flavonoids could be ranked, based on a decreased order, as biflavone, flavone, flavone glycoside, flavone biglycoside. The strategy is expected to be practical and useful for screening bioactive molecules from herbal medicines, especially for the minor compounds, which will definitely accelerate the discovery of new drug candidates.

Fractionating of green mandarin (Citrus deliciosa Tenore) essential oil by vacuum fractional distillation

This work aims to evaluate the technical viability of vacuum fractional distillation to separate the components of green mandarin (Citrus deliciosa Tenore) essential oil. Thermal degradation was also analyzed. The obtained results demonstrate that vacuum fractional distillation is capable to separate the hydrocarbon terpenes, which were removed from the top/stages of the column, from the terpenes with other chemical functions, which remained in the bottom. Some trace compounds, such as methyl-N-methyl anthranilate (mass fraction of 0,006 in the raw oil) and alpha sinensal (mass fraction of 0,004 in the raw oil), had their concentrations increased more than ten times after the separation, to mass fraction of 0,153 and 0,109, respectively. The mass fraction of the major compound of the essential oil, d-limonene, was reduced from 0,707 in the raw oil, to 0,218 in the bottom. There was no evidence of thermal degradation in the products of the separation.

Composition, Chemical Fingerprinting and Antimicrobial Assessment of Costa Rican Cultivated Guavas (Psidium friedrichsthalianum (O. Berg) Nied. and Psidium guajava L.) Essential Oils from Leaves and Fruits

The essential oil of two related tree species, P. friedrichsthalianum and P. guajava, where obtained. A total of six different oil samples were recovered including leaves in dry/rainy season and fruits of both plant species. Oil yields ranged between 0.128% (P. friedrichsthalianum leaves during dry season)-0.743% (P.guajava leaves during rainy season). All extracts were subjected to a GC/MS analysis using, during the chromatographic separation, a polyethylene glycol column. In general terms, we recognized three independent biosynthetic routes i. aromatic compounds ii. Terpenes and iii.Fatty acids derivatives. Several compound were found to be preserved in several of the oils such as 2,4-di-tert-butylphenol, α-terpineol and neointermedeol whereas Costa Rican guava fruit exhibit unique compounds such as 2H-pyran-2,6-(3H)-dione. Terpenes and fatty acids are among the most variable (p 0.1%) and trace compounds. In addition, we evaluated the antimicrobial activity of these essential oils against common foodborne and food-spoilage related bacteria. The rainy season P. guajava leafs’ presented the highest antimicrobial activity against all the bacteria strains tested, with inhibition zones ranging from 31 to 52 mm. This study will help understand volatile composition of a fruit producing plant native from this geographic area and hints toward possible applications.

Quantitative carbon detector for enhanced detection of molecules in foods, pharmaceuticals, cosmetics, flavors, and fuels.

Analysis of trace compounds, such as pesticides and other contaminants, within consumer products, fuels, and the environment requires quantification of increasingly complex mixtures of difficult-to-quantify compounds. Many compounds of interest are non-volatile and exhibit poor response in current gas chromatography and flame ionization systems. Here we show the reaction of trimethylsilylated chemical analytes to methane using a quantitative carbon detector (QCD; the Polyarc™ reactor) within a gas chromatograph (GC), thereby enabling enhanced detection (up to 10×) of highly functionalized compounds including carbohydrates, acids, drugs, flavorants, and pesticides. Analysis of a complex mixture of compounds shows that the GC-QCD method exhibits faster and more accurate analysis of complex mixtures commonly encountered in everyday products and the environment.

Detection of disease markers in human breath with laser absorption spectroscopy

AbstractNumber of trace compounds (called biomarkers), which occur in human breath, provide an information about individual feature of the body, as well as on the state of its health. In this paper we present the results of experiments about detection of certain biomarkers using laser absorption spectroscopy methods of high sensitivity. For NO, OCS, C

Limiting factors for planar solid oxide fuel cells under different trace compound concentrations

The present work investigates the performance of anode supported solid oxide fuel cells under the influence of different trace compounds. EIS (Electrochemical impedance spectroscopy) has been used to deconvolute the impedance spectra of an SOFC (Solid Oxide Fuel Cell) in order to identify the main losses. The impact of single and double contaminants on the SOFC performance has also been investigated. Typical biogas trace contaminants, obtained after a clean-up stage, such as sulfur, chlorine, aromatic compounds and siloxanes, have been taken into consideration. The results show how the ohmic contribution is almost independent of the H2S concentration. H2S acts mainly on the polarization losses and especially on the mass transport resistance. The impact of HCl on the SOFC performance is mainly connected to the charge transfer process. D4, as the model compound for siloxanes, already acts on SOFC performance at ppb(v) levels. The polarization losses have been influenced the most, and the largest increase has been recorded for the low frequency term, Rlow, related to the mass transport resistance for naphthalene and toluene. H2S, introduced with other contaminants, causes the instantaneous deterioration of the SOFC performance and the more the types of contaminants co-fed to the SOFC, the larger the initial anode degradation.

Plasmonic Trace Sensing below the Photon Shot Noise Limit

Plasmonic sensors are important detectors of biochemical trace compounds, but those that utilize optical readout are approaching their absolute limits of detection as defined by the Heisenberg uncertainty principle in both differential intensity and phase readout. However, the use of more general minimum uncertainty states in the form of squeezed light can push the noise floor in these sensors below the shot noise limit (SNL) in one analysis variable at the expense of another. Here, we demonstrate a quantum plasmonic sensor whose noise floor is reduced below the SNL in order to perform index of refraction measurements with sensitivities unobtainable with classical plasmonic sensors. The increased signal-to-noise ratio can result in faster detection of analyte concentrations that were previously lost in the noise. These benefits are the hallmarks of a sensor exploiting quantum readout fields in order to manipulate the limits of the Heisenberg uncertainty principle.

Adsorption of hydrogen sulfide (H2S) on zeolite (Z): Retention mechanism

Zeolites are efficient adsorbents for the removal of hydrogen sulfide (H2S) – a trace compound commonly found in biogas. The assessment of zeolite regeneration potential is an important point to consider before using them in adsorption processes for biogas treatment. In this study, it was first shown that after adsorption of H2S, by heating a 13X zeolite at 350°C, the desorbed quantities of sulfur compounds were very low. Afterwards, the objective was to understand H2S removal mechanism. Complementary physicochemical characterizations of the studied zeolite before and after H2S adsorption were performed: specific surface area, porosity, pH, infrared spectroscopy, thermogravimetry and differential scanning calorimetry. The speciation of sulfur in the studied zeolite after H2S adsorption was investigated and a retention mechanism was proposed. It was demonstrated that H2S was converted in elemental sulfur in the zeolite. This mechanism involves H2S adsorption at the zeolite surface, dissolution and dissociation of H2S in pore water, and oxidation to form elemental sulfur that can polymerize. The major formation of elemental sulfur limits the thermal regeneration of the studied zeolite and other regeneration methods should be considered.

Mass spectrometric profiling of valepotriates possessing various acyloxy groups from Valeriana jatamansi.

Valepotriates, plant secondary metabolites of the family Valerianaceae, contain various acyloxy group linkages to the valepotriate nucleus and exhibit significant biological activities. Identification of valepotriates is important to uncover potential lead compounds for the development of new sedative and antitumor drugs. However, making their structure elucidation by nuclear magnetic resonance (NMR) experiments is too difficult to be realized because of the overlapped carbonyl carbon signals of acyloxy groups substituted at different positions. Thus, the mass spectrometric profiling of these compounds in positive ion mode was developed to unveil the exact linkage of acyloxy group and the core of valepotriate. In this study, electrospray ionization tandem multistage mass spectrometry (ESI-MS/MS(n)) in ion trap and collision-induced dissociation tandem MS were used to investigate the fragmentation pathways of four types of valepotriates in Valeriana jatamansi, including 5-hydroxy-5,6-dihydrovaltrate hydrin (5-hydroxy-5,6-dihydrovaltrate chlorohydrin), 5,6-dihydrovaltrate hydrin (5,6-dihydrovaltrate chlorohydrin), 5-hydroxy-5,6-dihydrovaltrate and valtrate hydrin (valtrate chlorohydrin). The high-resolution mass spectrum (HRMS) data of all the investigated valepotriates from quadrupole time-of-flight MS/MS were used as a supportive of the fragmentation rules we hypothesized from ion-trap stepwise MS(n). As a result, the loss sequence of acyloxy groups and the abundance of key product ions, in combination with the characteristic product ions corresponding to the valepotriate nucleus, could readily differentiate the four different types of valepotriates. The summarized fragmentation rules were also successfully exploited for the structural characterization of three new trace valepotriates from V. jatamansi. The results indicated that the developed analytical method could be employed as a rapid, effective technique for structural characterization of valepotriates, especially for the trace compounds that could not be identified by NMR techniques. This study may also arouse interest for further structural analysis of other valepotriate-containing type herbal medicines.

Effective permeability of binary mixture of carbon dioxide and methane and pre-dried raw biogas in supported ionic liquid membranes

Abstract The influence of the temperature and stage cut on permeation of CO 2 and CH 4 through two different supported ionic liquid membranes were studied. The measurements were performed with binary mixture of CH 4 and CO 2 and with real pre-dried biogas collected in sewage plant. The influence of temperature on permeability followed the Arrhenius behavior in agreement with solution diffusion model of transport. The influence of stage cut was also very small, what helped to confirm that the membrane was operated under optimal conditions. The results obtained with real pre-dried biogas were very close to those obtained with the binary mixture. This was caused by the fact that the amount of trace compounds present in real pre-dried biogas was very small (less than 1 vol.%). The results showed that supported ionic liquid membranes (SILMs) can be used for biogas upgrading. It can be also concluded that the use of model mixture instead of real biogas for measurements brings relevant results.

Volatile trace compounds released from municipal solid waste at the transfer stage: Evaluation of environmental impacts and odour pollution

Odour pollution caused by municipal solid waste is a public concern. This study quantitatively evaluated the concentration, environmental impacts, and olfaction of volatile trace compounds released from a waste transfer station. Senventy-six compounds were detected, and ethanol presented the highest releasing rate and ratio of 14.76kg/d and 12.30g/t of waste, respectively. Life cycle assessment showed that trichlorofluoromethane and dichlorodifluoromethane accounted for more than 99% of impact potentials to global warming and approximately 70% to human toxicity (non-carcinogenic). The major contributor for both photochemical ozone formation and ecotoxicity was ethanol. A detection threshold method was also used to evaluate odour pollution. Five compounds including methane thiol, hydrogen sulphide, ethanol, dimethyl disulphide, and dimethyl sulphide, with dilution multiples above one, were considered the critical compounds. Methane thiol showed the highest contribution to odour pollution of more than 90%, as indicated by its low threshold. Comparison of the contributions of the compounds to different environmental aspects indicated that typical pollutants varied based on specific evaluation targets and therefore should be comprehensively considered. This study provides important information and scientific methodology to elucidate the impacts of odourant compounds to the environment and odour pollution.

Lubricity Improvement of the Ultra-low Sulfur Diesel Fuel with the Biodiesel

Ultra-low sulfur diesel fuel is essential requirement as per the emission regulation. With the adoption of hydrodesulfurization (HDS) process, the diesel fuel loses its inherent lubricity, however certain amount of lubricity of diesel fuel is needed to save several engine components from wear and failure. Though the loss of lubricity of the diesel fuel is observed with the removal of sulfur, it is mainly due to the loss of nitrogen and oxygen based polar trace compounds which are also removed in the HDS process. Unrefined biodiesels having little amount of monoglycerides (<0.8%) and free fatty acids also show better lubricity and fuel properties to be used as fuel lubricant. Biodiesel are also considered as the suitable blending compound with the diesel. This study found that the biodiesel blends up to 20% with the diesel fuel can effectively reduce both the wear of the tribo-contact surfaces as well as the friction coefficient. The use of biodegradable fuel lubricant has set away the threat of environment pollution by the diesel additives which are derived chemically. The oxidation stability and the low temperature properties of both the biodiesel and the vegetable oils can be improved with some chemical modification. It can be concluded that the use of biodiesel with the diesel fuel can be an appropriate option for effective engine lubrication system where only the fuel has to provide the required lubricity.

Comparison of adsorbents for H2S and D4 removal for biogas conversion in a solid oxide fuel cell

Biogas contains trace compounds detrimental for solid oxide fuel cell (SOFC) application, especially sulphur-containing compounds and volatile organic silicon compounds (VOSiCs). It is therefore necessary to remove these impurities from the biogas for fuelling an SOFC. In this paper, dynamic lab-scale adsorption tests were performed on synthetic polluted gas to evaluate the performance of a polishing treatment to remove hydrogen sulphide (H2S – sulphur compound) and octamethylcyclotetrasiloxane (D4 – VOSiC). Three kinds of adsorbents were tested: an activated carbon, a silica gel (SG) and a zeolite (Z). Z proved to be the best adsorbent for H2S removal, with an adsorbed quantity higher than at the SOFC tolerance limit. However, as concerns D4 removal, SG was the most efficient adsorbent, with an adsorbed quantity of about 184 mgD4/gSG at the SOFC tolerance limit. These results could not be explained by structural characteristics of the adsorbents, but they were partly explained by chemical interactions between the adsorbate and the adsorbent. In these experiments, internal diffusion was the controlling step, Knudsen diffusion being predominant to molecular diffusion. As Z was also a good adsorbent for D4 removal, competition phenomena were investigated with Z for the simultaneous removal of H2S and D4. It was shown that H2S retention was dramatically decreased in the presence of D4, probably due to D4 polymerization resulting in pore blocking.

Characterization of Mg&lt;sub&gt;0.8&lt;/sub&gt;Zn&lt;sub&gt;0.2&lt;/sub&gt;TiO&lt;sub&gt;3&lt;/sub&gt; Prepared via Liquid Phase Sintering

Mg0.8Zn0.2TiO3 powder was synthesized by dissolved method and calcined at 550 °C for 4 hours. The powder exhibited single phase of Mg0.8Zn0.2TiO3 and nano size particle. Sintered pellet samples were prepared by compacting calcined powder which contains 4wt% B2O3 (MZTA), 4wt% Bi2O3 (MZTB) as liquid additive and non-additive sample (MZTC). Phase identification and its percentage were analyzed based on XRD pattern using Rietveld method. The result shows major phase Mg0.8Zn0.2TiO3 ranging from 72.83% for MZTA, 77.9% for MZTB and 82.61% for MZTC. Furthermore, minor phases were identified as Mg2TiO4 and other trace compound Mg3TiO2(BO3)2 for boron additive. Sintered pellet densities were determined by Archimedes method indicate that Bi2O3 additive has the most effective for densification. Microstructure characterization using SEM show that MZTB possesses the largest grain size ≈3.4µm followed by MZTA 2.3µm and MZTC 1.78µm. Dielectrics characterizations within frequency 1 Hz – 32 MHz exhibited space charge polarization characteristic for frequency &lt;1 kHz, however for frequency &gt;1 kHz showed frequency independence of dipolar polarizations and low dielectric loss having εr~17.