Analysis Of Target Compounds Research Articles

Methods of analysis of glycoluril and its derivatives

The present work provides the literature data generalization concerning analysis of glycoluril, its derivatives and related compounds that allows obtaining information about the structure and properties of these com-pounds. Basic methods for analysis of glycoluril and substances on the basis thereof are considered, ad-vantages and disadvantages of these methods are described. The generalized results of the methods of analy-sis of glycoluril and its derivatives show that the majority of carried studies are focused on the revealing of purity and identification of related impurities for compounds that found practical application (drugs, mono-mers and polymers on the basis thereof). Consistent trend to active search of new methods to analyze macrocyclic and supramolecular systems synthesized on the basis of glycoluril is observed. The aim of the present review is to take attention of chemists to the most advanced methods of analysis of glycoluril and its derivatives with reference to promotion of further research. The literature analysis will be useful for research-ers dealing with designing of new molecules based on glycoluril with given properties where the methods of process control and analysis of target compounds has a decisive importance.

N-nitrosoethylenethiourea formation at environmentally-relevant concentrations of ethylenethiourea in a pooled groundwater sample

N-nitroso compounds form from the interaction between nitrosatable precursors and nitrite under acidic conditions. A majority of N-nitroso compounds tested show evidence of carcinogenicity in animal models. Formation of N-nitroso compounds may occur from exposure to precursors in drinking water, but the extent of formation depends on a number of factors, including concentration of substrates, presence of catalysts and inhibitors, and pH. The objective of this study was to examine these factors in pesticide-associated N-nitroso (PANN) compound formation in drinking water. In preliminary screening experiments, nine nitrosatable pesticides and degradation products were individually reacted at environmentally-relevant concentrations (≤ 20 μg L‐−1) with sodium nitrite (NaNO2) and hydrochloric acid (HCl) in ultra-pure water. Only ethylenethiourea (ETU) showed evidence of PANN compound formation in initial experiments and was further tested for N-nitrosoethylenethiourea (N-ETU) formation in a pooled groundwater sample (comprised of five tap water samples combined into one homogenous sample) collected from an agricultural region of Prince Edward Island in Canada, where nitrate contamination is a known concern. Evidence of N-ETU formation in the groundwater sample was observed within 30 min at concentrations 7.5, 10, and 20 μg L−1. Analysis of target compounds and semi-target PANN compounds was performed using ultra-high pressure liquid chromatography coupled with high resolution orbital ion trap mass spectrometry. These preliminary experiments serve to inform about potential PANN compound formation in groundwater. The results of this study suggest that ETU is capable of forming potentially carcinogenic N-ETU in water containing nitrite/nitrate at trace concentrations under acidic conditions. Thus, these findings suggest that N-ETU formation may be a concern for individuals exposed to low concentrations of ETU in groundwater.

Electrodialysis as a sample processing tool for bulk organic matter and target pollutant analysis of seawater

Electrodialysis (ED) is an advancing seawater sample processing tool that enables the separation of analytes from the often interfering salt matrix. In this study, we present the evaluation of a laboratory scale ED system for both dissolved organic matter (DOM) and target pollutant analysis of seawater.The developed sample processing protocol yields reproducible data and was found to be robust towards moderate changes in sample composition. At the final salinity of 0.1, the average recovery of DOM in the form of dissolved organic carbon, nitrogen and phosphorus (DOC, DON and DOP) was 44, 53 and 89%, respectively. DOM loss occurred mainly in the late stage of the ED process.When investigating specific ED processing parameters, it was discovered that the initial sample salinity does not influence DOM recovery. The final salinity, by contrast, is a dominant influence factor on DOM recovery. Furthermore, DOC and DOP recoveries could be improved by 8% by refining the electrical current in the ED cell. Surprisingly, adjustments of the sample pH did not lead to any improvements in DOM recovery.The experiments with target analytes showed that the recovery of individual molecules is determined by their n-octanol water partition coefficients logKow. High recoveries > 80% were achieved for compounds with medium logKow of −1 to 3. Hydrophobic compounds with logKow > 3 were lost through surface adsorption to the system walls and tubing. Small, polar and charged compounds with logKow < −1 are prone to loss via ED membrane passage, which occurred predominantly in the late stage of the ED process. Consequently, sample processing with ED was deemed beneficial for the LC-MS or GC–MS analysis of polar target compounds, because they are often difficult to enrich from seawater. Furthermore, during LC-MS or GC–MS analyses, matrix-dependent ion suppression was reduced in ED isolates, giving rise to increased signal responses of 25 to 620%, which resulted in improved instrumental sensitivity.

Target and suspect screening of substances liable to migrate from food contact paper and cardboard materials using liquid chromatography-high resolution tandem mass spectrometry

This work describes the analysis of both target and non-target compounds in paper and cardboard materials together with the characterization of their migration to Tenax® by means of liquid chromatography coupled to both low (LC-QqQ) and high resolution tandem mass spectrometry (LC-q-Orbitrap), respectively. To this aim, an entire analytical procedure was fully developed and validated for both matrices: paper/cardboard and Tenax®. A total of 97 chemicals, including photoinitiators, phthalates, biocides, antioxidants, etc., listed by the European Regulation, were found in the materials under study together with other substances not included in this list. Moreover, the majority of annotated substances were present in the simulant, giving evidence of their migration capacity. Migration percentages of 10 photoinitiators, 4 phthalates, bisphenol A, bis-(2-ethylhexyl) adipate, acetyltributyl citrate and caprolactam to Tenax® were quantified. Despite not exceeding the established specific migration limit (SML) in any case, benzophenone, 4-phenylbenzophenone and bisphenol A concentrations in some paper and cardboard materials were very close to the SML values established by the EU legislation.

Nontargeted Analysis of a Non-Aqueous-Phase Liquid From a Chemical Manufacturing Site Using Nuclear Magnetic Resonance Spectroscopy.

Non-aqueous-phase liquids (NAPLs), composed primarily of organic solvents and other immiscible liquids, can be found in the subsurface at many industrial sites. The chemical composition of NAPLs is often complex and, in many instances, difficult to fully characterize using conventional analytical techniques based on targeted compound analysis. Incomplete characterization of NAPLs leaves gaps in the understanding of the chemical profile at an impacted site. Previous work has shown that nuclear magnetic resonance (NMR) spectroscopy may be able to assist in the improved characterization of complex NAPL samples. In general, NMR spectroscopy provides an unbiased approach for the analysis of organic compounds because different classes of compounds are all treated and analyzed using the same methods. In addition, NMR spectroscopy provides unique structural information that can be used to elucidate unknowns. The present study describes the use of NMR spectroscopy as a nontargeted tool to characterize the composition of NAPLs collected from an impacted site. It is shown that NMR spectroscopy can be a complementary tool to be used in site assessments to help provide improved understanding of NAPL chemistry, leading to the development of improved conceptual site models and improved strategies for remedial and managerial activities at impacted sites. Environ Toxicol Chem 2019;00:1-9. © 2019 SETAC.

Towards multiproxy, ultra-high resolution molecular stratigraphy: Enabling laser-induced mass spectrometry imaging of diverse molecular biomarkers in sediments

Mass spectrometry imaging (MSI) collects mass spectra of organic compounds from individual micrometer-sized spots and yields high-resolution images of the spatial distribution of target analytes on sample surfaces. MSI can potentially open a new avenue to ultra-high resolution molecular stratigraphy by resolving the fine-scale distribution of molecular biomarkers in geological records. However, ionization of organic molecules within their sediment matrix remains a critical challenge. Building on the recent introduction of MSI of archaeal tetraether lipids, we have extended the analytical spectrum to additional biomarkers and provide guidelines for the generation of multiproxy, ultra-high resolution paleoenvironmental records. We evaluated the addition of artificial matrices to promote ionization, defined the most suitable MS settings, and increased analytical complexity from pure compounds to their investigation in sediment. Most compounds relevant to molecular stratigraphy are not properly ionized in the presence of conventional matrices, but require atypical ones, such as those based on carbon or silver. Sediments serve as a natural matrix, directly allowing detection of many of these compounds. However, the sediment matrix also inhibits some reactions that otherwise promote detection, such as derivatization of alkenones or silver-mediated ionization of n-alkanes. The robustness of MSI-based molecular stratigraphy is enhanced by analysis of target compounds in narrow m/z ranges, and by summation of mass spectra from several coeval measurement spots. We present an initial inventory of compounds readily detected in the sediment tested, including long chain alkenones and diols, sterols, and pigments, and provide an outlook into the use of MSI in multiproxy studies.

Development of drug discovery screening system by molecular interaction kinetics-mass spectrometry.

Drug discovery studies invariably require qualitative and quantitative analyses of target compounds at every stage of drug discovery. We have developed a system combining molecular interaction analysis and mass spectrometry (LC-MS) using the principle of nanopore optical interferometry (nPOI) called molecular interaction kinetics-mass spectrometry (MIK-MS). Since nPOI has high binding capacity, the bond-dissociated compound can be directly detected using LC-MS. In this study, we use carbonic anhydrase II (CAII) as a ligand and apply six small compounds as analytes and report the affinity analysis using MIK-MS. CAII was immobilized onto a COOH sensor chip using standard amine coupling. A reference surface was prepared by activating and subsequently blocking the surface under identical conditions. An amount of 50 μL of mix solution was injected over the reference channel and sample channel for CAII immobilization. The solutions eluting from the sensor chip were collected from the waste-line of the SKi Pro system every 30s. Reconstructed elution samples were then injected into the LC-MS/MS system. A mixture containing furosemide, acetazolamide, 4-sulfamoylbenzoic acid, 5-(dimethylamino)-1-naphthalene sulfonamide (DNSA), sulfanilamide and sulpiride (15 μM each) was injected into the CAII-immobilized sensor chip, and the fractions eluted from the SKi Pro system were collected and subjected to selected reaction monitoring LC-MS characterization. Specific results were obtained for acetazolamide, DNSA, furosemide and sulpiride. The results suggest that the association-dissociation curve of a mixed sample can be obtained by one-time MIK-MS analysis. Six small-molecule binders of CAII were analyzed quantitatively using nPOI and MIK-MS, and the results were compared to published surface plasmon resonance (SPR) results. The nPOI and SPR results show good agreement, confirming the reliability of the analysis. Time-dependent binding results may be obtained by our MS sensorgram approach. Drugs that meet medical needs in a short period are required; this nPOI-LC-MS system is considered an important tool for rapid drug discovery.

Monitoring the occurrence of pharmaceuticals in soils irrigated with reclaimed wastewater.

The use of reclaimed wastewater for irrigation is foreseen as a possible strategy to mitigate the pressure on water resources in dry regions. However, there is the risk of potential accumulation of contaminants of emerging concern (CECs) in the edaphic environment, their percolation and consequently contamination of aquifers. In the present study, we measured the levels of a wide range of commonly used pharmaceutically active compounds (PhACs) in sewage from a local wastewater treatment plant (WWTP) and in soils irrigated with treated wastewater. Analysis of target compounds showed total concentrations between 73 and 372 μg L-1 in WWTP influents, and from 3 to 41 μg L-1 in effluents. The total concentrations of PhACs detected in surface soil samples were in the range of 2 and 15 ng g-1, with predominance of analgesics and anti-inflammatories (maximum concentration = 10.05 ng g-1), followed by antibiotics and psychiatric drugs (maximum concentration = 5.45 ng g-1 and 3.78 ng g-1, respectively). Both effluent samples and irrigated soils shared similar compositional patterns, with compounds such as hydrochlorothiazide and diclofenac being predominant. Additionally, PhACs were also detected in soil samples at a depth of 150 cm, indicating that these chemical undergo leaching associated with heavy-rain episodes. Their occurrence in soils was affected by temperature too, as maximum concentrations were measured in colder months (up to 14 ng g-1), indicating higher persistence at lower temperatures. Finally, the ecotoxicological risk of PhACs in soil was evaluated by calculating their risk quotients (RQs). The risk was very low as RQ values ranged between <0.01 and 0.07. However, this initial assessment could be improved by future works on toxicity using specific terrestrial organisms.

High-Throughput Screening and Quantitation of Target Compounds in Biofluids by Coated Blade Spray-Mass Spectrometry.

Most contemporary methods of screening and quantitating controlled substances and therapeutic drugs in biofluids typically require laborious, time-consuming, and expensive analytical workflows. In recent years, our group has worked toward developing microextraction (μe)-mass spectrometry (MS) technologies that merge all of the tedious steps of the classical methods into a simple, efficient, and low-cost methodology. Unquestionably, the automation of these technologies allows for faster sample throughput, greater reproducibility, and radically reduced analysis times. Coated blade spray (CBS) is a μe technology engineered for extracting/enriching analytes of interest in complex matrices, and it can be directly coupled with MS instruments to achieve efficient screening and quantitative analysis. In this study, we introduced CBS as a technology that can be arranged to perform either rapid diagnostics (single vial) or the high-throughput (96-well plate) analysis of biofluids. Furthermore, we demonstrate that performing 96-CBS extractions at the same time allows the total analysis time to be reduced to less than 55 s per sample. Aiming to validate the versatility of CBS, substances comprising a broad range of molecular weights, moieties, protein binding, and polarities were selected. Thus, the high-throughput (HT)-CBS technology was used for the concomitant quantitation of 18 compounds (mixture of anabolics, β-2 agonists, diuretics, stimulants, narcotics, and β-blockers) spiked in human urine and plasma samples. Excellent precision (∼2.5%), accuracy (≥90%), and linearity (R2 ≥ 0.99) were attained for all the studied compounds, and the limits of quantitation (LOQs) were within the range of 0.1 to 10 ng·mL-1 for plasma and 0.25 to 10 ng·mL-1 for urine. The results reported in this paper confirm CBS's great potential for achieving subsixty-second analyses of target compounds in a broad range of fields such as those related to clinical diagnosis, food, the environment, and forensics.

Tchebichef-Hermite image moment method: A novel tool for chemometric analysis of three-dimensional spectra

Image moment methods have been applied to the qualitative and quantitative analyses in analytical chemistry owing to their availability. As another attractive image moment method, Tchebichef-Hermite moment (THM) method was proposed for the first time in this work, which originated from the Tchebichef moment method and Hermite moment method. The performances of the THM method were tested with two instances for the quantitative analysis of multiple target compounds on the basis of HPLC-PAD and LC-MS three-dimensional (3D) spectra, respectively. Experimental results indicate that the THM method not only inherits the common advantages of these discrete orthogonal moments to deal with some fundamental challenges (such as partially overlapped signals, uncalibrated interferences, peak shifts and baseline drifts) during the analytical process of different kinds of 3D spectra, but also has its unique superiority in information extraction ability that simplify the determination of optimum maximal orders in moment methods. Compared with the previously used Tchebichef moment method, THM method is much more convenient and efficient.

Determination of 17 Plant Growth Regulator Residues by Ultra-High Performance Liquid Chromatography-Triple Quadrupole Linear Ion Trap Mass Spectrometry Based on Modified QuEChERS Method

A new method combining modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) with ultra-high performance liquid chromatography-triple quadrupole linear ion trap mass spectrometry (UHPLC-QTrap-MS/MS) was developed for simultaneous determination of 17 plant growth regulator (PGR) residues in vegetables. Quantitative data acquisition was accomplished in multiple reaction monitoring (MRM) mode, and qualitative analysis and identification of target compounds was achieved by using linear ion trap scan functions. Qualitative and quantitative analysis can be simultaneously achieved by a pair of ions in UHPLC-QTrap-MS/MS. More importantly, QTrap system can minimize the risk of false positive and negative results. To achieve the optimum performance towards the target analytes, several parameters including the content of formic acid in mobile phase and scanning mode were investigated. In the optimized conditions, 17 PGRs showed good linearity over the range of 2~50 μg/L with correlation coefficients of 0.9902~0.9999. The limits of detections (LODs) were in the range of 0.01~1.32 μg/kg. The recoveries of 17 PGRs ranged from 78.5 to 119.2% with the spiked levels of 1, 2, and 5 μg/kg into homogenized radish, and the relative standard deviations (RSDs) ranged from 0.8 to 14.8%. The method illustrated is suitable for routine quantitative and qualitative analyses of PGRs in vegetable samples.

Simultaneous Determination of Multiple Persistent Halogenated Compounds in Human Breast Milk

Abstract A method was developed for simultaneous determination of multiple persistent organic pollutants (POPs) such as organochlorine pesticides (OCPs), hexabromocyclododecanes (HBCDs), polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs), in human breast milk. The sample pretreatment procedure included liquid-liquid extraction, gel permeation chromatography (GPC), and solid-phase extraction (SPE) cleanup. Gas chromatography-mass spectrometry (GC-MS), liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS) were applied in the analysis of target compounds. By using GPC to remove high-molecular-weight lipids and SPE for further cleanup and separation of target compounds, the interferences from the biological matrix could be greatly reduced. The developed sample pretreatment is suitable for multi-component analysis of very low concentrations of POPs in small volume of human samples. The developed method of simultaneous determination of PCBs and OCPs by GC-MS/MS exhibited excellent sensitivity and selectivity. Spiked recoveries were 88.7%–98.8% for PBDEs, 88.5%–92.5% for HBCDs, 67.9%–82.3% for PCBs, and 81.7%–116.1% for OCPs, and limits of detection were 0.13–1.8 ng L −1 for PBDEs, 0.31–1.2 ng L −1 for HBCDs, 0.22–1.4 ng L −1 for PCBs, and 0.20–1.5 ng L −1 for OCPs. This method was applied to the analysis of POPs in 20 human breast milk samples from Weifang City. The result showed that the median concentrations of HBCDs, PBDEs, PCBs, and OCPs were 2.86, 7.76, 8.84 and 643 ng g −1 lipid weight, which were comparable to those in human breast milk samples from populations of other regions in China.

Simultaneous analysis of bisphenol A based compounds and other monomers leaching from resin-based dental materials by UHPLC-MS/MS.

Resin-based dental materials have raised debates concerning their safety and biocompatibility, resulting in a growing necessity of profound knowledge on the quantity of released compounds into the oral cavity. In this context, the aim of this study was to develop a comprehensive and reliable procedure based on liquid chromatography with mass spectrometry for the simultaneous analysis of various leached compounds (including bisphenol A based compounds) in samples from in vitro experiments. Different experiments were performed to determine the optimal analytical parameters, comprising mass spectrometry parameters, chromatographic separation conditions, and sample preparation. Four internal standards were used as follows: deuterated diethyl phthalate and bisphenol A (commercially available), and deuterated analogues of triethylene glycol dimethacrylate and urethane dimethacrylate (custom-made). The optimized method was validated for linearity of the calibration curves and the associated correlation coefficient, lower limit of quantification, higher limit of quantification, and intra- and interassay accuracy and precision. Additionally, the developed liquid chromatography with tandem mass spectrometry method was applied to the analysis of leaching compounds from four resin-based dental materials. The results indicated that this method is suitable for the analysis of different target compounds leaching from dental materials. This method might serve as a valuable basis for quick and accurate quantification of leached compounds from resin-based dental materials in biological samples.

Laboratory performance study for passive sampling of nonpolar chemicals in water.

Two laboratory performance studies with 21 and 11 participants were carried out for passive sampling of nonpolar chemicals in water, using silicone samplers that were deployed for 7 wk and 13 wk at 2 river sites in the Netherlands. Target analytes were polychlorinated biphenyls, polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs), hexachlorobutadiene, hexachlorobenzene, and a number of performance reference compounds (PRCs). Calculation of aqueous concentrations based on prescribed input values and a prescribed uptake model was also included. Between-laboratory coefficients of variation (CVs) in the analysis of target compounds were approximately 20% at concentrations of 100 ng g-1 and approximately 100% at concentrations of 0.01 ng g-1 , which was similar to previous results for the analysis of biota samples. The analysis of PRCs yielded water sampling rates with a between-laboratory CV of 18% to 30%. The sampling rate model showed a nearly perfect match with the consensus values of retained PRCs. The implications of the present study for future interlaboratory exercises are discussed. Environ Toxicol Chem 2017;36:1156-1161. © 2016 SETAC.

Interpreting comprehensive two-dimensional gas chromatography using peak topography maps with application to petroleum forensics.

BackgroundComprehensive two-dimensional gas chromatography (GC times GC) provides high-resolution separations across hundreds of compounds in a complex mixture, thus unlocking unprecedented information for intricate quantitative interpretation. We exploit this compound diversity across the (GC times GC) topography to provide quantitative compound-cognizant interpretation beyond target compound analysis with petroleum forensics as a practical application. We focus on the (GC times GC) topography of biomarker hydrocarbons, hopanes and steranes, as they are generally recalcitrant to weathering. We introduce peak topography maps (PTM) and topography partitioning techniques that consider a notably broader and more diverse range of target and non-target biomarker compounds compared to traditional approaches that consider approximately 20 biomarker ratios. Specifically, we consider a range of 33–154 target and non-target biomarkers with highest-to-lowest peak ratio within an injection ranging from 4.86 to 19.6 (precise numbers depend on biomarker diversity of individual injections). We also provide a robust quantitative measure for directly determining “match” between samples, without necessitating training data sets.ResultsWe validate our methods across 34 (GC times GC) injections from a diverse portfolio of petroleum sources, and provide quantitative comparison of performance against established statistical methods such as principal components analysis (PCA). Our data set includes a wide range of samples collected following the 2010 Deepwater Horizon disaster that released approximately 160 million gallons of crude oil from the Macondo well (MW). Samples that were clearly collected following this disaster exhibit statistically significant match (99.23 pm 1.66 ),% using PTM-based interpretation against other closely related sources. PTM-based interpretation also provides higher differentiation between closely correlated but distinct sources than obtained using PCA-based statistical comparisons. In addition to results based on this experimental field data, we also provide extentive perturbation analysis of the PTM method over numerical simulations that introduce random variability of peak locations over the (GC times GC) biomarker ROI image of the MW pre-spill sample (sample #1 in Additional file 4: Table S1). We compare the robustness of the cross-PTM score against peak location variability in both dimensions and compare the results against PCA analysis over the same set of simulated images. Detailed description of the simulation experiment and discussion of results are provided in Additional file 1: Section S8.ConclusionsWe provide a peak-cognizant informational framework for quantitative interpretation of (GC times GC) topography. Proposed topographic analysis enables (GC times GC) forensic interpretation across target petroleum biomarkers, while including the nuances of lesser-known non-target biomarkers clustered around the target peaks. This allows potential discovery of hitherto unknown connections between target and non-target biomarkers.Electronic supplementary materialThe online version of this article (doi:10.1186/s13065-016-0211-y) contains supplementary material, which is available to authorized users.

Characterization of the chemical composition of white chrysanthemum flowers of Hangzhou by using high-performance ion trap mass spectrometry.

In this study, high-performance liquid chromatography coupled with amaZon SL high-performance ion trap mass spectrometry was used to analyze the target components in white chrysanthemum flowers of Hangzhou. Twenty-one components were detected and identified in both white chrysanthemum flowers of Hangzhou samples by using target compound analysis. Furthermore, seven new compounds in white chrysanthemum flowers of Hangzhou were found and identified by analyzing the fragment ion behavior in the mass spectra. The established method can be expedient for the global quality investigation of complex components in herbal medicines and food.

Environmental pollution of polybrominated diphenyl ethers from industrial plants in China: a preliminary investigation

Although numerous studies have shown the presence of polybrominated diphenyl ethers (PBDEs) in various environmental media, attention to their distribution in the environmental media surrounding industrial facilities is limited. In this study, eight PBDEs congeners (BDE-28, -47, -99, -100, -153, -154, -183, -209) were investigated in surface soils and water samples collected from commercial PBDE manufacturers, flame-retardant plastic modification plants and waste electrical and electronic equipment recycling facilities in China. Analysis of target compounds was performed using the model NCI GC-MS in SIM mode. The concentrations of ∑8PBDEs varied from 193.1 to 22,004.3 ng/L in water samples and from 1209.3 to 226,906 ng/g dry wt in surface soils, respectively. More severe PBDE contamination, when compared with previously reported data, was found in industrial areas in this study. This indicates that these industrial areas are highly polluted with PBDEs. BDE-209 was the predominant congener, accounting for more than 94% in this study, except for a 68.75% portion at one site. Our results show that PBDE manufacturing and flame-retardant plastic modification plants, easily overlooked by the public, are two primary PBDE pollution sources although they affect surrounding areas. Further research is needed, aimed at managing industrial PBDE emissions and eliminating environmental PBDE pollution, to investigate the material flows and environmental fates of PBDEs in all stages of the life cycle.

Volatile organic compound emissions from an engine fueled with an ethanol-biodiesel-diesel blend

With the advent of energy crisis, vehicle engines need alternative energy sources eagerly to supply power. Ethanol-biodiesel-diesel blends are considered to be effective solutions. One way is diesel engines burning blended fuels. Diesel engines exhaust many kinds of volatile organic compounds (VOCs) when mixed fuels burn in them. Extremely poisonous as these VOCs are, they can cause severe damage to the natural environment as well as human health. To explore the characteristics of the unregulated emissions produced by diesel engines and then to limit them, research and studies should be conducted. The research in this paper used a single-cylinder diesel engine and a chromatograph mass spectrometer to investigate 9 kinds of VOCs (benzene, toluene, n-butyl acetate, ethylbenzene, p-xylene, m-xylene, styrene, o-xylene, n-undecane) emissions of ethanol-biodiesel-diesel (EBD) and diesel (D). The solid phase adsorption-thermal desorption-gas chromatography mass spectrometry (GC/MS) had an advantage in measuring and analyzing VOC emissions, so it was used for investigating the total emissions of 9 kinds of VOCs. Based on the standard curves of VOCs, the GC/MS computed the peak area of each VOC and realized the quantitative analysis of target compounds. By the calculating equation of VOC specific emissions and other test parameters (exhaust flow, engine power, dilution ratio, test time), the test got VOC specific emissions of two different fuels under different operating conditions. The test selected five typical conditions to collect exhaust when burning EBD and D. EBD contained 10 vol. % ethanol, 30 vol. % biodiesel, 55 vol. % diesel, 2.5 vol. % n-butyl alcohol and 2.5 vol. % iso-octyl alcohol, which had strong stabilities and good economy. From the analysis of the test results of VOC emissions, it was found that EBD increased total emissions by 84.2% at rated power but decreased by 14.85% at 10% load and by 20.39% at 50% load compared with diesel. But under other test conditions, VOC emissions with EBD were lower than diesel. VOC emissions of the two fuels were mainly benzene and toluene at medium and high load, which increased up to 47.4%. Emissions of other components increased at low load. In general, it was possible to decrease VOC emissions at medium or low loads when the diesel engine was fueled with EBD. The ozone specific reactivities (SR) of the engine exhaust for the two test fuels were approximately the same for the selected operating conditions. The SRs of EBD were a bit lower than D at medium and low loads. EBD had an advantage relative to VOC emissions which was found mainly at medium and low loads. This study is valuable for contributing to the building of a VOC emissions standard and for demonstrating the potential benefit of substitute fuels in reducing VOCs.

Dispersive liquid-liquid microextraction: trends in the analysis of biological samples.

Dispersive liquid-liquid microextraction (DLLME) is a recent microextraction technique that was first developed by Rezaee and co-workers in 2006. It allows the simultaneous extraction and preconcentration of analytes into a micro-volume of extracting solvent based on a ternary solvent system involving an aqueous phase, a nonpolar water immiscible high-density solvent that acts as extraction phase, and a disperser solvent, which is often polar and water miscible. This article presents an overview of DLLME applications in the analysis of biological samples (e.g., plasma and urine). Aside from the classical DLLME applications using high density extraction solvents, recent advances in the use of low density solvents and ionic liquids are also discussed. Although most of the applications deal with the analysis of organic target compounds, a few applications on the bioanalysis of inorganic substances are also included.

High-speed counter-current chromatography coupled online to high performance liquid chromatography–diode array detector–mass spectrometry for purification, analysis and identification of target compounds from natural products

A challenge in coupling high-speed counter-current chromatography (HSCCC) online with high performance liquid chromatography (HPLC) for purity analysis was their time incompatibility. Consequently, HSCCC–HPLC was conducted by either controlling HPLC analysis time and HSCCC flow rate or using stop-and-go scheme. For natural products containing compounds with a wide range of polarities, the former would optimize experimental conditions, while the latter required more time. Here, a novel HSCCC–HPLC–diode array detector–mass spectrometry (HSCCC–HPLC–DAD–MS) was developed for undisrupted purification, analysis and identification of multi-compounds from natural products. Two six-port injection valves and a six-port switching valve were used as interface for collecting key HSCCC effluents alternatively for HPLC–DAD–MS analysis and identification. The ethyl acetate extract of Malus doumeri was performed on the hyphenated system to verify its efficacy. Five main flavonoids, 3-hydroxyphloridzin (1), phloridzin (2), 4′,6′-dihydroxyhydrochalcone-2′-O-β-d-glucopyranoside (3, first found in M. doumeri), phloretin (4), and chrysin (5), were purified with purities over 99% by extrusion elution and/or stepwise elution mode in two-step HSCCC, and 25mM ammonium acetate solution was selected instead of water to depress emulsification in the first HSCCC. The online system shortened manipulation time largely compared with off-line analysis procedure and stop-and-go scheme. The results indicated that the present method could serve as a simple, rapid and effective way to achieve target compounds with high purity from natural products.