Interaction between natural organic matter (NOM) and polycyclic aromatic compounds (PAC) – comparison of fluorescence quenching and solid phase micro extraction (SPME)

The interaction of phenanthrene and 9-aminophenanthrene with natural organic matter (NOM) of different origin was investigated using the fluorescence quenching approach and the solid phase micro extraction method. The results of both methods are compared in terms of the influence of the concentration of the polycyclic aromatic compounds (PAC) as well as the concentration of the NOM on the observed binding constant. Due to the combination of steady-state and time-resolved fluorescence techniques it could be concluded that the observed fluorescence quenching was caused by a static interaction like a complex formation. While for phenanthrene both analytical methods showed no long term effects and the reaction equilibrium between NOM and phenanthrene was established within the first hour, for 9-aminophenanthrene a slow reaction kinetics (within days) was found indicating specific interactions between NOM and the amino group. Received: 12 November 1998 / Revised: 22 December 1998 / Accepted: 30 December 1998     

An ionic liquid-based sorbent for solid phase extraction of trace iron(Ш) from biological and natural water samples

A new ionic liquid modified silica gel sorbent was prepared from the reaction of active silica gel with N-3-(-3-triethoxysilylepropyl)-3-methylimidazolium chloride ([(TESP)MIm]Cl). This sorbent was exploited as solid phase extractant for separation and preconcentration of metal ions prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). It was found that it can selectively adsorb Fe(Ш). Identification of the surface modification was performed on the basis of FT-IR. Experimental conditions for effective adsorption of trace Fe(Ш) were optimised using both batch and column procedures. At pH 3, Fe(Ш) could be quantitatively adsorbed and completely eluted by using 2?mL of 0.1?mol?L^?1 of HCl. 150?mL of sample solution was adopted as the maximum sample volume and a high enrichment factor of 75 was obtained. Most common coexisting ions did not interfere with the separation and preconcentration of Fe(Ш) at optimal conditions. The maximum static adsorption capacity of the sorbent was 37.0?mg?g^?1. The detection limit of the present method was 0.48?µg?L^?1, and the relative standard deviation (R. S. D.) was lower than 1.7%. The method was successfully applied to the preconcentration of trace Fe(Ш) in biological and natural water samples with satisfactory results.     

Ultrasound-assisted extraction and on-line LC–GC–MS for determination of polycyclic aromatic hydrocarbons (PAH) in urban dust and diesel particulate matter

A method has been developed for determination of polycyclic aromatic hydrocarbons (PAH) in particulate matter from ambient air and diesel exhaust emissions. It is reproducible and accurate and, compared with similar methods for analysis of individual PAH components in complex matrices, it is relatively fast and simple. Single PAH components can be determined in samples of particulate matter from ambient air and diesel exhaust emissions with LOD of approximately 1 pg/sample. Further, sample throughput is high, because more than 20 samples can be extracted and prepared for analysis in one working (8-h) day. The particulate matter is subjected to ultrasound-assisted extraction, a technique that is shown to extract PAH from particulate material with efficiencies fully comparable with those of Soxhlet extraction. An aliphatic/PAH-enriched fraction is obtained by solid-phase extraction before isolation, separation, and identification/quantification of PAH by on-line liquid chromatography–gas chromatography–mass spectrometry. The method was validated by analysis of US National Institute of Standards and Technology (NIST) Standard Reference Materials (SRM) 1649a, Urban Dust, and 2975, Diesel Particulate Matter. Results from the method are in good agreement with the NIST-certified PAH concentrations and with NIST reference PAH concentrations.     

π-hole bonding: A new retention mechanism for the solid phase extraction of polycyclic aromatic hydrocarbons from the hexane extracts of soil samples

In this work, the perfluorobenzene-bonded silica sorbent was tested to adsorb polycyclic aromatic hydrocarbons in hexane. In the comparison experiments, the perfluorobenzene-bonded sorbent's performance was better than octadecyl silica sorbent and phenyl-bonded silica sorbents, which indicated that the π-hole···π bonds between perfluorobenzene and the polycyclic aromatic hydrocarbons were stronger than π···π interactions and hydrophobic interactions in hexane. Then the perfluorobenzene-bonded silica sorbent was applied to solid-phase extraction of 15 polycyclic aromatic hydrocarbons from the hexane extracts of soil samples directly without the solvent replacement, which simplified the soil pretreatment process. And the results showed that under the optimal conditions, the proposed method for the determination of polycyclic aromatic hydrocarbons in the environment soil presented good recoveries and stabilities for the 10 heavier polycyclic aromatic hydrocarbons with the recoveries ranging from 75.1% to 104.6% and the relative standard deviations being in the range of 1.4%–5.8%. The limits of detection of the method varied from 0.1 to 2 ng/g. This work reveals the great application potential of the π-hole bond as a new retention mechanism in the field of solid-phase extraction.     

Solid-phase micro extraction (SPME) and headspace derivatization of clenbuterol followed by GC–FID and GC–SIMMS quantification

Solid-phase micro extraction (SPME) and on-fiber derivatization followed by Gas Chromatography coupled with Flame Ionization Detection (GC-FID) or Selected Ion Monitoring Mass Spectrometry (GC-SIMMS) allows for simple yet sensitive quantification for the hexamethyldisilazane derivative of the beta-agonist clenbuterol. Using an 85- micro m polyacrylate fiber, the analysis method is optimized with respect to extraction time, derivatization time and temperature, and solution pH. In addition, the use of a rapid temperature ramping injection port allows for optimization of fiber desorption conditions. Under optimal conditions, the limits of detection for the hexamethyldisilazane derivative of clenbuterol are 1.1 ppb by FID and 0.20 ppb by SIMMS.     

High performance liquid chromatography–tandem mass spectrometry for the analysis of 10 pesticides in water: A comparison between membrane-assisted solvent extraction and solid phase extraction

This work describes the application of two sample preparation methods: membrane-assisted solvent extraction (MASE) and solid phase extraction (SPE) in combination with high performance liquid chromatography–tandem mass spectrometry (HPLC–MS–MS) for the determination of 10 pesticides in surface and ground water. Optimal extraction conditions for MASE were 60 min extraction time at 30 °C with a solvent volume of 100 μL toluene. 5 μL of the toluene extract were directly injected in the HPLC–MS–MS system. Concerning SPE, two materials were tested and C18 was superior to Oasis HLB. Complete desorption was ensured by desorbing the SPE (C18) cartridge with 3 mL of an acetonitrile/methanol mixture (1:1). After evaporation, the extract was injected in the analytical system. Analyte breakthrough was not found for the investigated compounds. For both methods, high extraction yields were achieved, in detail 71% (metalaxyl) till 105% (linuron) for MASE and 52% (ethiofencarb) till 77% (prometryne) for SPE (C18). Detection limits were in the low ng/L range for both methods and precision, expressed as the relative standard deviation (RSD) of the peak areas was below 13%. Five real water samples were analyzed applying both extraction methods. The results were in good agreement and standard addition proved that no matrix effects (such as ion suppression) occurred. In this comparison SPE has the potential of larger sensitivity whereas faster analysis and slightly better recoveries were achieved with MASE. MASE shows potential to be a promising alternative to the conventional off-line SPE concerning low to medium polar compounds.     

Determination of pesticides by solid phase extraction followed by gas chromatography with nitrogen–phosphorous detection in natural water and comparison with solvent drop microextraction

The European Union specificies that drinking water can contain pesticide residues at concentrations of up to 0.1 μg/L each and 0.5 μg/L in total, and that 1–3 μg/L of pesticides can be present in surface water, but the general idea is to keep discharges, emissions and losses of priority hazardous substances close to zero for synthetic substances. Therefore, in order to monitor pesticide levels in water, analytical methods with low quantification limits are required. The method proposed here is based on solid phase extraction (SPE) followed by gas chromatography with a nitrogen–phosphorous detector (GC-NPD). During method development, six organophosphate pesticides (azinphos-ethyl, chlorfenvinphos, chlorpyriphos, ethoprophos, fenamiphos and malathion) and two organonitrogen pesticides (alachlor and deltamethrin) were considered as target analytes. Elution conditions that could influence the efficiency of the SPE were studied. The optimized methodology exhibited good linearity, with determination coefficients of better than 0.996. The analytical recovery for the target analytes ranged from 70 to 100%, while the within-day precision was 4.0–11.5 %. The data also showed that the nature of the aqueous matrice (ultrapure, surface or drinking water) had no significant effect on the recovery. The quantification limits for the analytes were found to be 0.01–0.13 μg/L (except for deltamethrin, which was 1.0 μg/L). The present methodology is easy, rapid and gives better sensitivity than solvent drop microextraction for the determination of organonitrogen and organophosphate pesticides in drinking water at levels associated with the legislation.     

Experimental determination and prediction of (solid + liquid) phase equilibria for binary mixtures of aromatic and fatty acids methyl esters

Solid–liquid equilibria for binary mixtures of {methyl stearate (1) + biphenyl (2)}, {methyl stearate (1) + naphthalene (2)}, {methyl palmitate (1) + biphenyl (2)} and {methyl palmitate (1) + naphthalene (2)} were measured using differential scanning calorimeter. Simple eutectic behaviours for these systems were observed. The experimental results were correlated by means of the NRTL, Wilson, UNIQUAC and ideal models. The root-mean-square deviations of the solubility temperatures for all measured data vary from 0.5477 K (for UNIQUAC model) to 7.79 K; the deviations depend on the binary system studied and particular model used. The best solubility correlation was obtained with UNIQUAC model and this observation confirms previous results.     

Chemistry of natural compounds and bioorganic chemistry Synthesis of (±)-furodizinin and (±)-furodizin

The racemic forms of natural Omnoterpenoids, (±)-furodizinin and (±)-furodizin, were synthesized by cationic cyclization of the or -furylmethyl derivatives of linalool, geraniol and nerol.A. M. Moiseenkov (1936–1992), an outstanding Russian organic chemist, would have been sixty on July 6, 1996, He contributed significantly to the chemistry of terpenoids. The scientific heritage of A, M. Moiseenkov is rich and diversified. This work is devoted to the walizWon of one of his ideas. For the preliminary communication see Ref. 1.DeceasedTranslated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1842–1847, July, 1996.     

Identification and quantification of odorous compounds from adhesives used in food packaging materials by headspace solid phase extraction and headspace solid phase microextraction coupled to gas chromatography–olfactometry–mass spectrometry

Adhesives are often responsible for off-flavors in food in contact with packaging. The aim of this investigation was to identify by GC–O–MS the odorous compounds in five different types of adhesive (hotmelt, vinyl acetate ethylene, starch, polyvinyl acetate and acrylic) used in food packaging. In order to obtain a substantial number of compounds, they were extracted by two complementary extraction methods: HS-SPE and HS-SPME. Fifteen minutes extraction time using PDMS fiber for hotmelt adhesive and DVD/CAR/PDMS fiber for the other adhesives were the best conditions for defining a representative solvent-free adhesive extract using a rapid and simple D-GC–O technique. Thirty-three compounds were identified by GC–O–MS. These include butyric acid, acetic acid, methyl butyrate, 1-butanol and nonanal, which were present in most of the adhesives under study producing cheesy, rancid, sour, medicinal and green aromas, respectively. The concentrations were determined, the most abundant compound being acetic acid with concentrations from 22.9 to 8930 μg g⁻¹ of adhesive.     

Determination of oxygenated and native polycyclic aromatic hydrocarbons in urban dust and diesel particulate matter standard reference materials using pressurized liquid extraction and LC–GC/MS

The objective of this study was to develop a novel analytical chemistry method, comprised of a coupled high-performance liquid chromatography–gas chromatography/mass spectrometry system (LC–GC/MS) with low detection limits and high selectivity, for the identification and determination of oxygenated polycyclic aromatic hydrocarbons (OPAHs) and polycyclic aromatic hydrocarbons (PAHs) in urban air and diesel particulate matter. The linear range of the four OPAHs, which include 9,10-anthraquinone, 4H-cyclopenta[def]phenanthrene-4-one, benzanthrone, and 7,12-benz[a]anthraquinone, was 0.7 pg–43.3 ng with limits of detection (LODs) and limits of quantification (LOQs) on the order of 0.2–0.8 and 0.7–1.3 pg, respectively. The LODs in this study are generally lower than values reported in the literature, which can be explained by using large-volume injection. The recoveries of the OPAHs spiked onto glass fiber filters using two different pressurized liquid extraction (PLE) methods were in the ranges of 84–107 and 67–110 %, respectively. The analytical protocols were validated using the following National Institute of Standards and Technology standard reference materials: SRM 1649a (Urban Dust), SRM 1650b (Diesel Particulate Matter), and SRM 2975 (Diesel Particulate Matter, Industrial Forklift). The measured mass fractions of the OPAHs in the standard reference materials (SRMs) in this present study are higher than the values from the literature, except for benzanthrone in SRM 1649a (Urban Dust). In addition to the OPAHs, 44 PAHs could be detected and quantified from the same particulate extract used in this protocol. Using data from the literature and applying a two-sided t test at the 5 % level using Bonferroni correction, significant differences were found between the tested PLE methods for individual PAHs. However, the measured mass fractions of the PAHs were comparable, similar to, or higher than those previously reported in the literature.     

Synthesis and characterization of cellulose-g-polyoxyethylene (2) hexadecyl ether solid–solid phase change materials

A series of novel solid–solid phase change materials, namely, cellulose-g-polyoxyethylene (2) hexadecyl ether (Cellulose-g-E₂C₁₆) copolymers, were synthesized using toluene 2,4-diisocyanate (TDI) as a coupling reagent in the ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). The optimum prepolymerization conditions were determined to be 25 °C and 75 min without catalyst, and the optimum reaction conditions of the grafting step were 90 °C, 6 h and 0.1 wt% dibutyltin dilaurate (DBTDL, weight percent of TDI). The successful grafting was confirmed by FTIR and ¹H-NMR. The properties of the Cellulose-g-E₂C₁₆ copolymers were investigated by DSC, TG and XRD. It is shown that the heat storage ability and phase change temperature of Cellulose-g-E₂C₁₆ copolymers depended on the degree of substitution. The crystalline type of the grafted E₂C₁₆ was not affected by the cellulosic backbone. Compared with E₂C₁₆, Cellulose-g-E₂C₁₆ copolymers showed better thermal stability. They are expected to be widely applied in the area of thermal energy storage.     

ZrIV metal–organic framework based on terephthalic acid and 1,10-phenanthroline as an adsorbent for solid phase extraction of tetracycline antibiotics

Zr^IV metal–organic framework based on terephthalic acid and 1,10-phenanthroline has been prepared by solvothermal method. The product represents an effective adsorbent for solid phase extraction of tetracycline antibiotics from aqueous media.     

π-Selective stationary phases: (III) Influence of the propyl phenyl ligand density on the aromatic and methylene selectivity of aromatic compounds in reversed phase liquid chromatography

The retention characteristics of phenyl type stationary phases for reversed phase high performance liquid chromatography are still largely unknown. This paper explores the retention process of these types of stationary phases by examining the retention behaviour of linear PAHs and n-alkylbenzenes on a series of propyl phenyl stationary phases that have changes in their ligand density (1.23, 1.31, 1.97, 2.50 μmol m⁻²). The aromatic and methylene selectivities increased with increasing ligand density until a point where a plateau was observed, overall the propyl phenyl phases had a higher degree of aromatic selectivity than methylene selectivity indicating that these columns are suitable for separations involving aromatic compounds. Also, retention characteristics relating to the size of the solute molecule were observed to be influenced by the ligand density. It is likely that the changing retention characteristics are caused by the different topologies of the stationary phases at different ligand densities. At high ligand densities, the partition coefficient became constant.     

Trace analysis of pentachlorophenol (PCP) in wood and wood-based products – comparison of sample preparation procedures

The main problem with routine analyses of pentachlorophenol (PCP) and sodium pentachlorophenolate (Na-PCP) in wood and wood-based products is to determine critical PCP-contents. This task requires a reliable analytical method and statistical testing. An analytical procedure is described, which permits the determination of PCP and Na-PCP with sufficient sensitivity and accuracy. A medium size sieve (4 × 4 mm quadratic mesh) was found suitable for the grinding step. Different extraction techniques and solvents were tested systematically. Extraction by a combination of ultrasonication and shaking in the solvent mixture toluene/sulfuric acid showed best recoveries. The eluted PCP and Na-PCP were derivatized with acetic anhydride and determined by GC/ECD. The limits of detection and determination were 0.14 mg/kg and 0.40 mg/kg, respectively. Received: 6 August 1999 / Revised: 26 October 1999 / Accepted: 1 November 1999     

Relationship between (micro)structure and functional (photocatalytic and adsorption) properties of anatase–mordenite nanocomposite

Research on Chemical Intermediates - Anatase–mordenite nanocomposite was synthesized in situ and characterized by X-ray diffraction analysis, Brunauer–Emmett–Teller...     

Interaction of volatile organic compounds (VOCs) emitted from banana on stanene nanosheet—a first-principles studies

Using ab initio calculation, structural stability, including electronic properties of bare/hydrogenated stanene (BSn/HSn) nanosheet, was explored. The geometrical stability of HSn material is verified with the influence of phonon band structure and formation energy. The concentration of the present work is to check the quality of Musa acuminata (banana) fruits when it is in ripe and overripe stage using HSn nanosheet material. Further, the interaction of different volatile organic compounds, namely, isoamyl acetate, isobutyl acetate, acetoin, and 2,3-butanediol aromas on HSn base material is studied with the significant parameter such as Bader charge transfer, band gap, adsorption energy, and average energy band gap changes. The sensitivity of the aromas emitting from ripe and overripe stages of banana on HSn nanosheet was studied using density of states spectrum. The adsorption energy of HSn nanosheet is found in the range of ??0.055 to ??0.989 eV upon the interaction VOCs of Musa acuminata. The novel aspect of the present work is to check the quality of Musa acuminata with the influence of HSn nanosheet using density functional theory.     

Solid phase extraction�Cinductively coupled plasma spectrometry for adsorption of Co(II) and Ni(II) from radioactive wastewaters by natural and modified zeolites

Natural and modified clinoptilolite as low-cost adsorbents have been used for adsorption of Co(II) and Ni(II) from nuclear wastewaters both in batch and continuous experiments. Zeolite X was also synthesized and its ability towards the selected cations was examined. Kinetic and thermodynamic behaviors for the process were investigated and adsorption equilibrium was interpreted in term of Langmuir and Freundlich equations. The effect of various parameters including the initial concentration, temperature, ionic strength and pH of solution were examined to achieve the optimized conditions. The clinoptilolite was shown good sorption potential for Co(II) and Ni(II) ions at pH values 4?C6. Based on desorption studies, nearly 74 and 85% of adsorbed Co(II) and Ni(II) were removed from clinoptilolite by HCl. The Na⁺ and NH₄ ⁺ forms of clinoptilolite were the best modified forms for the removal of investigated cations. It is concluded that the selectivity of clinoptilolite is higher for Co(II) than Ni(II). The synthesized zeolite showed more ability to remove cobalt and nickel ions from aqueous solution than the natural clinoptilolite. The microwave irradiation was found to be more rapid and effective for ion exchange compared to conventional ion exchange process.     

Synthesis, crystal structures and fluorescence properties of four mixed-ligands Zn(Ⅱ) and Cd(Ⅱ) coordination compounds

Four new coordination compounds, [Zn(dba)(bpy)]n (1), {[Zn(dba)(phen)]·2H2O}n (2), [Cd(dba)(bpy)(H2O)2] (3) and [Cd2(dba)2(phen)2]n (4) (H2dba = 2,5-dihydroxy-p-benzenediacetic acid, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline) have been prepared via solvothermal method and characterized by sin-gle-crystal X-ray diffraction, infrared spectroscopy, elemental analysis and powder X-ray diffraction. 1 and 2 possess 1D infinite chain structures. Complex 3 exhibits a mononuclear structure. Complex 4 owns bi...