Analysis of volatile compounds of wild gilthead sea bream (Sparus aurata) by simultaneous distillation–extraction (SDE) and GC–MS

The volatile compounds of wild gilthead sea bream (Sparus aurata) were analyzed by sensory and instrumental analyses. Simultaneous distillation and extraction (SDE) with dichloromethane were used for extraction of volatile components. According to sensory analysis, the aromatic extract obtained by SDE was representative of sea bream odour. A total of 46 compounds were identified and quantified in sea bream. Aldehydes and alcohols were the most dominant volatiles in sea bream, as they accounted for the largest proportion. Hexanal, heptanal, nonanal, (Z)-4-heptenal, octanal, (E)-2-nonenal, decanal, benzenacetaldehyde, (E,E)-2,4-decadienal, 1-octen-3-ol and (E)-1,5-octadien-3-ol were potent aroma compounds on the basis of odour activity values (OAVs). Within these, decanal (OAV: 1110) and (E)-2-nonenal (OAV: 447.5) were the most powerful contributors to the aroma of the sea bream.     

Substoichiometric extraction of tantalum with diantipyrylmethane

Diantipyrylmethane is used for substoichiometric extraction of tantalum from 1—4M hydrofluoric acid into 1,2-dichlorethane. The selectivity of the method is good, niobium and antimony(V) being the main inteferences. The stoichiometric composition of the tantalum/diantipyrylmethane complex is 1:1. The method was usef for the determination of trace amounts of tantalum (0.52 ± 0.05 μ g^?1) in a lake sediment (Bodensee/Lake Constance) by neutron activation/μ-spectrometry. Tantalum was determined in niobium samples by an isotope dilution procedure after separation of the matrix on a polyurethane foam column loaded with diantipyrylmethane.     

Gas chromatography coupled with atomic absorption spectrometry — a sensitive instrumentation for mercury speciation

New instrumentation for the speciation of mercury is described, and is applied to the analysis of natural water samples. The separation of mercury species is effected using gas chromatography of derivatized mercury species on a widebore capillary column. The solvent is vented using a bypass valve and the separated mercury species are pyrolysed on-line at 800°C for production of mercury atoms. These are then detected by atomic absorption spectrometry (AAS) at the 253.7 and 184.9 nm lines simultaneously in a quartz cuvette. The use of the 184.9 nm line provides a more than five-fold increase in sensitivity compared with the conventional 253.7 nm line and an absolute detection limit of 0.5 pg of mercury. The dynamic range of the combined analytical lines provides a linear response over more than three orders of magnitude. A number of organic compounds not containing mercury are also detected following pyrolysis, especially at the 184.9 nm line. These background species must not co-elute at the retention times for methyl- and inorganic mercury, as otherwise a positive interference would result. By maximizing the chromatographic resolution and minimizing the band broadening in the cuvette by use of a make-up gas, the retention times of interest are freed from co-eluting background peaks.The instrumentation has been applied to the determination of ng l⁻¹ concentrations of methyl- and inorganic mercury in Lake Constance, Germany and within the Lake Constance drinking water supply organization, Bodenseewasserversorgung (BWV). The accuracy for the sum of methyl- and inorganic mercury has been assessed by comparison with an independent method for total mercury based on AAS detection implemented at BWV. Relative detection limits using 1 litre water samples and 15 ml injections of the final hexane extract were 0.03 ng l⁻¹ for methylmercury and 0.4 ng l⁻¹ for inorganic mercury based on the 3j criterion.     

Installation of Kayzero-INAA standardization in the TNRC and its applications for trace elements determination in different materials

The paper focuses on the validation of the k ₀-method of instrumental neutron activation analysis (k ₀-INAA) in the Tajura Nuclear Research Center (TNRC) via the analysis of several certified reference materials. The selected reference materials were: SRM 1572 Citrus Leaves, SRM 1575 Pine Needles, IAEA-A11 Milk Powder, IAEA-V-10 Hay Powder, RM IAEA-Soil-7 and RM IAEA-SL-1 Lake Sediment. The method is based on the PC version Kayzero/Solcoi software package issued by DSM. All the samples, reference materials and monitors were irradiated in various positions of the Tajura reactor with different f and α. The parameters f and α (f — thermal/epithermal neutron flux ratio, α — parameter accounting for the non-ideality of the 1/E epithermal neutron fluence rate distribution) were determined using the bare triple monitor method. The results obtained for all the reference materials are in good agreement with the certified values.     

Determination and distribution of polycyclic aromatic hydrocarbons in native vegetable oils,smoked fish products,mussels and oysters,and bream from the river Elbe

Twenty eight native vegetable oils were analyzed for polycyclic aromatic hydrocarbons. Generally PAH concentrations were low, but olive oils showed significantly higher contamination by light PAH ranging from 53 to 105.6 μg/kg. Muscle and liver samples of bream from the river Elbe contained little or no detectable amounts of PAH, whereas fresh and canned oysters and mussels showed higher contaminations. Highest PAH concentrations have been determined in “smoked oysters in oil” with 75.8 μg/kg benzo[a] pyrene for the oil and 12.2 μg/kg for the oyster meat.     

Certification of methylmercury content in two fresh-frozen reference materials: SRM 1947 Lake Michigan fish tissue and SRM 1974b organics in mussel tissue (Mytilus edulis)

This paper describes the development of two independent analytical methods for the extraction and quantification of methylmercury from marine biota. The procedures involve microwave extraction, followed by derivatization and either headspace solid-phase microextraction (SPME) with a polydimethylsiloxane (PDMS)-coated silica fiber or back-extraction into iso-octane. The identification and quantification of the extracted compounds is carried out by capillary gas chromatography/mass spectrometric (GC/MS) and inductively coupled plasma mass spectrometric (GC/ICP-MS) detection. Both methods were validated for the determination of methylmercury (MeHg) concentrations in a variety of biological standard reference materials (SRMs) including fresh-frozen tissue homogenates of SRM 1946 Lake Superior fish tissue and SRM 1974a organics in mussel tissue (Mytilus edulis) and then applied to the certification effort of SRM 1947 Lake Michigan fish tissue and SRM 1974b organics in mussel tissue (Mytilus edulis). While past certifications of methylmercury in tissue SRMs have been based on two independent methods from the National Institute of Standards and Technology (NIST) and participating laboratories, the methods described within provide improved protocols and will allow future certification efforts to be based on at least two independent analytical methods within NIST.     

A thermo extraction–UV/Vis spectrophotometric method for total iodine quantification in soils and sediments

Iodine in soils and sediments is a difficult element to analyze due to its volatility in acidic conditions. Traditionally it has been quantified using neutron activation analysis techniques, which, unfortunately, requires access to a nuclear reactor. We present here a simple method for solid-phase iodine analysis by thermo extraction at 1000°C and quantification by UV/Vis photometry. Samples are combusted in an oxygen stream and trapped in Milli-Q water. The extracts are then quantified by an As³⁺–Ce⁴⁺ spectrometric method whereby iodide catalyzes the oxidation of As³⁺ to As⁵⁺ and reduction of Ce⁴⁺ to Ce³⁺. Three standard reference materials were analyzed with excellent recoveries (97–113%) and RSDs (<5%). Moreover, the detection limit was less than 50 ng absolute iodine with a confidence limit of 95%. When applied to carbonate-rich samples from sediment traps deployed in Lake Constance we found very low iodine levels (0.8–2 mg kg⁻¹). Despite the low concentrations, the precision of the method was consistently better than 5% RSD. However, the method needed to be slightly modified for organic and iodine-rich sediments (20–30% organic carbon) from a lake in the Black Forest by increasing the oxygen flow rate and decreasing the combustion time. Using the modified method we were able to achieve RSDs lower than 5%.     

中空结构的双金属有机骨架材料作为固相微萃取纤维涂层用于多环芳烃的高灵敏检测

环境样品中多环芳烃(PAHs)含量较低且样品基质复杂,直接利用仪器进行含量测定比较困难,因此在仪器分析之前需要对环境样品进行必要的前处理。大多数前处理技术的萃取效率取决于萃取材料的特性。目前,金属有机骨架材料(MOFs)作为一种由金属离子与有机配体自组装而成的多孔材料,已经被用作固相微萃取(SPME)的涂层材料应用于PAHs的萃取,但是这些MOFs涂层材料由于目标物较难达到其深层的吸附位点,使得萃取过程往往需要较长的平衡时间;此外,大多数MOFs由单金属离子配位构成,能够提供的开放金属活性位点种类比较单一,较难获得最佳的萃取性能。这些问题在一定程度上限制了MOFs材料在SPME领域的应用。该研究制备了一种中空结构的双金属有机骨架材料(H-BiMOF),并将其作为SPME的涂层材料,用于萃取环境样品中痕量的PAHs。由于中空的结构和双金属的组成,H-BiMOF涂层材料拥有比表面积利用率高、传质距离短等优点,可以使萃取过程快速地达到平衡。同时,双金属的引入提供了种类丰富的金属活性位点,提高了对PAHs这类富电子云目标物的萃取效率。与气相色谱-串联质谱(GC-MS/MS)相结合,建立了一种用于环境水样中PAHs分析的新方法。所建立的分析方法具有检出限低(0.01~0.08 ng/L)、线性范围宽(0.03~500.0 ng/L)、重复性良好(相对标准偏差≤9.8%, n=5)等优点,并成功地用于实际湖水样品中7种PAHs的检测。实验结果表明,所建立的分析方法适用于环境样品中PAHs的分析与监测。     

Determination of polyfluoroalkyl phosphoric acid diesters, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, perfluoroalkyl carboxylic acids, and perfluoroalkane sulfonic acids in lake trout from the Great Lakes region

A comprehensive method to extract perfluoroalkyl carboxylic acids, perfluoroalkane sulfonic acids, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, and polyfluoroalkyl phosphoric acid diesters simultaneously from fish samples has been developed. The recoveries of target compounds ranged from 78?% to 121?%. The new method was used to analyze lake trout (Salvelinus namaycush) from the Great Lakes region. The results showed that the total perfluoroalkane sulfonate concentrations ranged from 0.1 to 145?ng/g (wet weight) with perfluorooctane sulfonate (PFOS) as the dominant contaminant. Concentrations in fish between lakes were in the order of Lakes Ontario ≈ Erie > Huron > Superior ≈ Nipigon. The total perfluoroalkyl carboxylic acid concentrations ranged from 0.2 to 18.2?ng/g wet weight. The aggregate mean perfluorooctanoic acid (PFOA) concentration in fish across all lakes was 0.045?±?0.023?ng/g. Mean concentrations of PFOA were not significantly different (p?>?0.1) among the five lakes. Perfluoroalkyl phosphinic acids were detected in lake trout from Lake Ontario, Lake Erie, and Lake Huron with concentration ranging from non-detect (ND) to 0.032?ng/g. Polyfluoroalkyl phosphoric acid diesters were detected only in lake trout from Lake Huron, at levels similar to perfluorooctanoic acid.     

Distribution of global fallout237Np,Pu isotopes,and241Am in lake and sea sediments

In order to investigate the sedimentary behaviour of neptunium,²³⁷Np together with Pu isotopes and²⁴¹Am have been measured for the sediment cores collected from Lake Mikata (freshwater) and from Lake Kugushi (brakish water) both belonging to the Mikata Five Lakes, and from Nyu Bay (sea water). In all sediment core samples²³⁷Np was detected, and its concentrations were far below those of^239,240Pu and²⁴¹Am measured for the same samples. Inventories of²³⁷Np in Lake Mikata, Lake Kugushi and Nyu Bay were estimated to be 0.53, 0.29 and 0.34 MBq/km², respectively. The activity ratio of²³⁷Np/^239,240Pu calculted from the inventories in each sediment core was 0.29% for Lake Mikata, 0.15% for Lake Kugushi and 0.10% for Nyu Bay. These values except for the value for Lake Mikata are two or three times lower than the value of 0.3–0.4% observed for surface soils of 0–20 cm depth, suggesting that Np is more soluble compared with Pu.     

Organochlorine Pesticides in Water,Sediment and Fish from the Nile River and Manzala Lake in Egypt

Abstract

To assess the risks of organochlorine pesticides discharged into the hydrospheric environment of Egypt, river and lake water, drinking water, suspended solids, sediments and fish were collected during 1993—1994 from the Nile River and Manzala Lake in Egypt and were transported to Japan for chemical analysis. Among different organochlorine pesticides analyzed, p,p′-DDE was the most predominant in fish (7.6 to 67 ng/g wet wt.), sediments (3.2 to 432 ng/g dry wt.) and suspended solids (5.3 tc 138 pg/L). However, in the dissolved phase of water samples HCH compounds predominated (α-HCH, 71 to 2,815 pg/L). Concentrations of organochlorine pesticides, except chlordane, were higher in Manzala Lake than in the River Nile. Concentrations of organochlorine pesticides in fish corresponded with those in sediments from each location. Comparison of organochlorine concentrations in Nile River water with those reported in earlier studies suggested a decrease in concentrations during the last decade. However, concentrations of p,p′-DDE has increased in fish. It appears that the release of this metabolite from contaminated sediment is the major source of p,p′-DDE in fish during recent years.     

Substituent effect on the molecular stability, group interaction, detonation performance, and thermolysis mechanism of nitroamino-substituted cyclopentanes and cyclohexanes

Density functional theory (DFT) method has been employed to study the effect of nitroamino group as a substituent in cyclopentane and cyclohexane, which usually construct the polycyclic or caged nitra-mines. Molecular structures were investigated at the B3LYP/6-31G** level, and isodesmic reactions were designed for calculating the group interactions. The results show that the group interactions ac-cord with the group additivity, increasing with the increasing number of nitroamino groups. The dis-tance between substituents influences the interactions. Detonation performances were evaluated by the Kamlet-Jacobs equations based on the predicted densities and heats of formation, while thermal stability and pyrolysis mechanism were studied by the computations of bond dissociation energy (BDE). It is found that the contributions of nitroamino groups to the detonation heat, detonation velocity, detonation pressure, and stability all deviate from the group additivity. Only 3a, 3b, and 9a-9c may be novel potential candidates of high energy density materials (HEDMs) according to the quantitative cri-teria of HEDM (ρ≈ 1.9 g/cm3, D ≈ 9.0 km/s, P ≈ 40.0 GPa). Stability decreases with the increasing number of N-NO2 groups, and homolysis of N-NO2 bond is the initial step in the thermolysis of the title com-pounds. Coupled with the demand of thermal stability (BDE > 20 kcal/mol), only 1,2,4-trinitrotriazacy-clohexane and 1,2,4,5-tetranitrotetraazacyclohexane are suggested as feasible energetic materials. These results may provide basic information for the molecular design of HEDMs.     

Photolyases and Cryptochromes in UV‐resistant Bacteria from High‐altitude Andean Lakes

“High‐altitude Andean Lakes” (HAAL) are pristine environments harboring poly‐extremophilic microbes that show combined adaptations to physical and chemical stress such as large daily ambient thermal amplitude, extreme solar radiation levels, intense dryness, alkalinity, high concentrations of arsenic (up to 200 ppm) and dissolved salts. In this work, we compared the UV resistance profiles, pigment content and photoreactivation abilities of three UV‐resistant bacteria isolated from distinct niches from HAALs, that is Acinetobacter sp. Ver3 (water, Lake Verde; 4400 m), Exiguobacterium sp. S17 (stromatolite, Lake Socompa, 3570 m) and Nesterenkonia sp. Act20 (soil, Lake Socompa, 3570 m). UV resistance ability of HAAL's strains indicate a clear adaptation to high radiation exposure encountered in their original habitat, which can be explained by genetic and physiological mechanisms named as the UV‐resistome. Thus, the UV‐resistome depends on the expression of a diverse set of genes devoted to evading or repairing the damage it provoked direct or indirectly. As pigment extraction and photoreactive assays indicate the presence of photoactive molecules, we characterized more in detail proteins with homology to photolyases/cryptochromes members (CPF). Phylogenetic analyses, sequence comparison and 3D modeling with bona fide CPF members were used to prove the presence of functional domains and key residues in the novel proteins.     

Chemical Composition of Hydrilla Verticillata （L. f.） Royle in Taihu Lake

Hydrilla verticillata （Linn. f.） Royle is a submerged plant for phytoremediation on Taihu Lake, China. The planted submerged plant should be harvested in every autumn to reduce the nutrition burden of the lake. Five compounds were firstly isolated by column chromatography and purified from the extractions of Hydrilla verticillata （Linn. f.） Royle. 1-（5＇-Hydroxy-4＇-hydroxymethyl-1＇-methyl-1H-pyrrol-2＇-yl）-henicosa-2,12,15-trien-1-one （2） and thymidine （3） were identified by EIMS, 1H NMR, laC NMR and IR spectra. Crystal loliolide （1） and sulfur-gamma （4） were identified by X-ray diffraction. Octadecanedioic acid （5） was also elucidated. Among them, compound 2 is a new natural compound, loliolide （1） and thymidine （3） are known bioactive substances. The results provided basic research data for exploring their application as medical materials.     

Synthesis,Photophysics, and Electroluminescence of Poly(dibenzofluorene)s

Summary: A series of soluble poly(dibenzofluorene) derivatives that contain dibenzo[a,g]fluorene, dibenzo[a,i]fluorene, and dibenzo[c,g]fluorene repeat units in the main chain have been synthesized, characterized, and explored as emissive materials in polymer light emitting diodes (PLEDs). These polymers possess higher glass transition temperatures (108–133 °C) than that of poly(2,7‐(9,9‐dialkyl)fluorene) (PFO). The photophysical and electrochemical properties of these polymers are affected by the steric hindrance effect. These polymers emit blue light in dilute solution (378–400 nm) and in the solid state (426–447 nm). As emissive materials in PLEDs, blue electroluminescence with a brightness of up to 3 130 cd · m⁻² is obtained from single‐layer diodes of P₂ with aluminum/barium in air.

The photophysical and electrochemical properties of these polymers are affected by the size effect.     

Depth-specific and spatiotemporal variation of δ13C and δ15N in Charophytes of Lake Constance: implications for food web studies

Macrophytes are at the base of many lake food webs providing essential food resources for animals at higher trophic level, such as invertebrates, fish and waterbirds. However, data regarding the spatiotemporal variation in isotopic composition of macrophytes are generally missing. We measured the carbon and nitrogen stable isotope ratios of Charophytes at Lake Constance, where they constitute a major food source for waterbirds. Our data reveal seasonal and site-specific differences as well as depth-specific variations in isotopic carbon values within the littoral zone. Charophytes were enriched in (13)C at sites of higher productivity: the δ(13)C values were high in summer, at shallow and at relatively nutrient-rich sites, and comparatively low in winter, and in deeper and nutrient-poorer sites. In contrast, no temporal or spatial trend was found to explain the variability in the isotopic nitrogen values. These results imply that the seasonal timing of food intake (relative to turnover rates of consumers tissue) and the potential depth of foraging need to be taken into account when calculating the relative contribution of energy sources to diets of consumers such as waterbirds.     

Application of membrane inlet mass spectrometry for online and in situ analysis of methane in aquatic environments

A method is presented for the online measurement of methane in aquatic environments by application of membrane inlet mass spectrometry (MIMS). For this purpose, the underwater mass spectrometer Inspectr200-200 was applied. A simple and reliable volumetric calibration technique, based on the mixing of two end member concentrations, was used for the analysis of CH₄ by MIMS. To minimize interferences caused by the high water vapor content, permeating through the membrane inlet system into the vacuum section of the mass spectrometer, a cool-trap was designed. With the application of the cool-trap, the detection limit was lowered from 100 to 16 nmol/L CH₄. This allows for measurements of methane concentrations in surface and bottom waters of coastal areas and lakes. Furthermore, in case of membrane rupture, the cool-trap acts as a security system, avoiding total damage of the mass spectrometer by flushing it with water. The Inspectr200-200 was applied for studies of methane and carbon dioxide concentrations in coastal areas of the Baltic Sea and Lake Constance. The low detection limit and fast response time of the MIMS allowed a detailed investigation of methane concentrations in the vicinity of gas seepages.     

鱼组织中双去甲氧基姜黄素、去甲氧基姜黄素和姜黄素含量的超高效液相色谱法测定

建立了黄颡鱼、团头鲂和草鱼血浆、肌肉、肝脏、肾脏中双去甲氧基姜黄素、去甲氧基姜黄素和姜黄素同时测定的超高效液相色谱紫外检测法(UPLC-UV)。样品经乙腈(含0.01%乙酸)提取,无水硫酸钠除水,正己烷去脂等样品处理,在ACQUIT UPLC BEH C18色谱柱上分离,428 nm波长处测定。双去甲氧基姜黄素、去甲氧基姜黄素和姜黄素在0.01~5.00 mg/L浓度范围内呈良好的线性关系,相关系数(r2)分别为0.998 7,0.999 8和0.999 6。在空白鱼组织中进行0.025,0.05,0.50,1.00 mg/kg 4个水平的加标回收实验,3种待测组分的平均回收率为64.7%~102.2%,相对标准偏差为0.69%~10.8%。鱼组织中3种待测组分的检出限(LOD)均为0.010 mg/kg,定量下限(LOQ)均为0.025 mg/kg。应用该方法研究了姜黄素在团头鲂体内的药代动力学规律。     

Effect of solvent type on polycondensation of TEOS catalyzed by DBTL as used for stone consolidation

We have investigated the effect of solvent in the sol–gel process of tetraethylorthosilicate (TEOS) when di-n-butyltin dilaurate (DBTL) is used as polycondensation catalyst. Two sets of materials similar to those employed in the field of stone consolidation were prepared in the laboratory by using either protic or aprotic solvents: (1) xerogels from TEOS/DBTL, and (2) composites from TEOS/colloidal silica particles/DBTL. The results have shown that the solvent directly influences the aggregation pathway of the condensates. For a mixture of methyl ethyl ketone/acetone (aprotic solvents), gels with a higher degree of condensation were obtained. In the case of TEOS xerogels, the materials are essentially non-porous. Additionally, the incorporation of colloidal silica particles induces an important increase in porosity, which is even more dramatic when ethanol is used as solvent, through the formation of micro and mesoporous materials as the concentration of particles is increased. A TEOS polymerization pathway is suggested depending on which system of solvents is used. Various analytical techniques were used to characterize the materials obtained.