Gamma-radiolysis and ozonolysis of polycyclic aromatic hydrocarbons (PAHs) in solution

Summary The degradation of a mixture of 18 different polycyclic aromatic hydrocarbons (PAHs) has been studied in acetonitrile solution by usingg-radiation at radiation doses of 100, 200 and 300 kGy. The mixture of radiolyzed PAHs was analyzed by liquid chromatography (HPLC) using a diode array detector. Radiolysis at 100 kGy total dose is already sufficient to cause the complete disappearance of all PAHs with the exception of fluorene and crysene which still survive in small amounts. They are known to be among the most radiation-resistant PAHs and can be completely eliminated from the radiolyzed solution by a treatment with ozone. Alternatively higher radiation dose (200 kGy) is needed to eliminate fluorene and crysene completely from the acetonitrile solution. PAHs can be degraded completely with an excess of ozone but the distribution of products is of course different from that obtained by radiolysis and radiolysis followed by ozonolysis.     

Evaluation of various collection phases for polycyclic aromatic hydrocarbons (PAH)

Summary Particle-bound and gaseous polycyclic aromatic hydrocarbons (PAH), some of which are strongly carcinogenic, can be detected as components of pyrolysis products of organic materials and are emitted at the place of work during certain manufacturing processes.An assessment of the risk to exposed workers depends on the determination of as wide a spectrum of PAH in the atmosphere as possible. Their quantitative collection on glass fibre filters causes problems because of the high volatility of PAH.A suitable collection system for air sampling of these substances has been sought on the basis of _n = 20 chosen PAH.Employing the phase equilibrium method and a simulated sampling process in a stream of nitrogen with PAH-coated collection phases it was possible to demonstrate a collection efficiency for volatile PAH of 82.7 to 105.7% on the adsorbing resin Tenax and of 82.9 to 103.9% on XAD-2 using toluene as eluent. Silica gel and Polygosil proved unsuitable as PAH adsorbents.An extremely effective sampling system suitable for the evaluation of the total PAH concentration at work places consists of the combination of a glass fibre filter as a collector for particulate PAH followed by an adsorption tube containing either Tenax or XAD-2 as back-up system for trapping the vapour-phase PAH.

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Bewertung verschiedener Sammelphasen für polycyclische aromatische Kohlenwasserstoffe (PAH)

Zusammenfassung Partikel-gebundene und gasförmige polycyclische aromatische Kohlenwasserstoffe (PAH) mit teilweise ausgeprägten carcinogenen Eigenschaften können als Bestandteile von Pyrolyseprodukten aus organischem Material bei bestimmten Fertigungsprozessen am Arbeitsplatz emittiert werden.Eine Risikoabschätzung exponierter Arbeitnehmer orientiert sich vorwiegend an Luftmessungen eines möglichst umfassenden PAH-Spektrums. Ihre quantitative Probenahme mittels Glasfaserfilter stößt wegen unterschiedlich ausgeprägter Flüchtigkeit der PAH auf Schwierigkeiten.Anhand von n = 20 ausgewählten Referenzsubstanzen wird ein geeignetes Sammelsystem im Probenahmeverfahren für PAH evaluiert.Durch Anwendung der sog. phase equilibrium method und des simulierten Probenahmeverfahrens mittels im Stickstoffstrom mit PAH beaufschlagter Sammelphasen konnten Überführungsraten für die gasförmigen PAH von 82,7 bis 105,7% an den Adsorberharzen Tenax und von 82,9 bis 103,9% an XAD-2 mit Toluol als Elutionsmittel erhalten werden. Nicht geeignet erwiesen sich Silicagel und Polygosil.Eine repräsentative Probenahme zur Abschätzung der PAH-Totalkonzentration ist bei einer kombinierten Anwendung von Glasfaserfilter als Sammelphase für partikuläre PAH und nachgeschaltetem Adsorptionsrohr mit wahlweise Tenax oder XAD-2 als Sorbens für gasförmige PAH als äußerst effektiv zu bezeichnen.

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Supported by the Bundesministerium für Forschung und Technologie of the Federal Republic of Germany, Project-No. 01 VD 093.     

Unprecedented use of silver(I) N-heterocyclic carbene complexes for the catalytic preparation of 1,2-bis(boronate) esters

Catalytic diboration of internal and terminal alkenes with Ag(I) N-heterocyclic carbene complexes leads to 1,2-bis(boronate) esters as single intermediates, that can be oxidised towards the corresponding diols.     

Laser-induced fluorescence of pyrene and other polycyclic aromatic hydrocarbons (PAH) in seawater

Polycyclic aromatic hydrocarbons (PAH) in the marine environment are currently of great concern due to their potential carcinogenicity. The standard methods of detection and quantification of PAH in seawater and sediments are costly, time-consuming and do not account for the heterogeneous nature of their distribution and sources. Laser-induced, time-resolved fluorescence spectroscopy may help to overcome these limitations. Several PAH have relatively long-lived stimulated fluorescence emissions, which allow them to be detected among a background of more intense but shorter-lived chromophores. Using time-delayed techniques we have shown an ability to detect PAH, principally pyrene, at environmental levels (ng l(-1)) both in the laboratory and in situ in Boston Harbor and other study areas. Further development may lead to the rapid determination of several PAH in typical near-shore marine environments.     

Determination of polycyclic aromatic hydrocarbons (PAHs) and total fats in human milk

A sensitive and reliable analytical method was developed for the simultaneous extraction of PAHs and total fats and their determination in the human milk. The method involved a liquid-liquid extraction of PAHs and fats, followed by the gravimetric determination of the latter. PAHs were separated from lipids by size exclusion chromatography eluting with methylene chloride and analysed by gaschromatography coupled with mass spectrometry (GC/MS). The recovery of analytes was in the range of 42-101% and agreed well with their boiling temperatures (R2=0.779). Precision of the method was found between 7.6 and 19%. Quantification and detection limits for individual PAHs ranged from 0.011 to 0.032 and from 0.006 to 0.022 microg/Kg milk (wet weight), respectively. Quantification limit for the total fat determination was 0.26 g/Kg milk (wet weight). This procedure, applied to milk samples of ten healthy, non-smoking, Italian primiparae, living in rural or low-traffic zones, allowed for the identification and quantitative determination of naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, benzo(b)fluoranthene and benzo(k)fluoranthene in the mean concentration range 0.114-6.95 microg/Kg milk (wet weight). The most volatile compounds, which were not investigated elsewhere, were found at much higher concentrations than those observed for the others. No relation was found between PAH and total fat concentrations.     

The physico-chemical speciation of polycyclic aromatic hydrocarbons (PAH) in aquatic systems

Summary Physico-chemical speciation is presented as a concept to describe the environmental chemistry of organic compounds in aquatic systems, using polycyclic aromatic hydrocarbons as an example.Survey data and experimental results are reported which demonstrate the presence of different physico-chemical species of PAH in the Tamar Estuary, UK.The degree, and hence chemistry of binding of PAH to particulates in the Tamar is shown to be incompatible with current sorption modelling techniques. This finding has extensive repercussions on prediction of the aquatic chemistry of PAH, including availibility of the compounds for fates such as photo-oxidation and biological uptake/ toxicity.

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Die physikalisch-chemische Speziation polycyclischer aromatischer Kohlenwasserstoffe (PAH) in aquatischen Systemen

Zusammenfassung Die physikalisch-chemische Speziation wird dargestellt zur Beschreibung der Umweltchemie organischer Verbindungen in aquatischen Systemen. Dabei dienen die PAH als Beispiel. Es werden Meßergebnisse und experimentelle Befunde gegeben, die die Anwesenheit verschiedener physikalisch-chemischer Spezien von PAH in der Mündung des Tamar-Flusses (UK) demonstrieren. Es wird gezeigt, daß der Grad und damit der Chemismus der Teilchenbindung von PAH im Tamarfluß nicht den üblichen Sorptionsmodellen entspricht. Diese Feststellung hat beträchtliche Auswirkungen auf die Voraussehbarkeit des aquatischen Chemismus der PAH einschließlich der Verfügbarkeit dieser Verbindungen für Photooxidation und biologische Aufnahme (Toxizität).

     

Photochemical degradation of polycyclic aromatic hydrocarbons (PAH) in real and laboratory conditions

Studies were carried out on the effects induced by the main components of airborne particulate matter (APM) as soot, inorganic and cyclohexane soluble substances and by glass fiber filters on photodegradation of pyrene, benz(a)anthracene and benzo(a)pyrene exposed to UV and solar radiation. In both experimental models tested hydrocarbons showed a higher photochemical stability when absorbed on APM. Inorganic components of APM slightly enhance UV photodegradation. In real condition (outdoor exposure to solar radiation) PAH half lives generally showed a good linear correlation with mean solar radiation intensity; only degradation rate of benzo(a)pyrene on APM, exposed to sunlight was practically constant. Pyrene, in particular, showed a higher degradation rate when high ozone concentrations (0.2 ppm) occurred.     

Progress in the analytical research methods of polycyclic aromatic hydrocarbons (PAHs)

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are one species of persistent organic pollutants (POPs) with strong carcinogenicity and teratogenicity. They can be widely found in the environment, which cause great harm to the ecological environment. In addition, they endanger human health by polluting food from the natural environment and food processing. Therefore, it is necessary to accurately detect PAHs in various sample matrices, which requires the accurate, practical and rapid detection methods. This review aims to investigate the progress of research methods for PAHs, including pretreatment methods and detection methods. A summary analysis of different methods is performed by searching the literature on numerous methods for detecting PAHs published in various journals. There are many pretreatment methods for PAHs, such as solid phase extraction (SPE), cloud point extraction (CPE) and so on. The most commonly used methods for detecting PAHs are high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). Spectrophotometry, chromatography and chromatography-mass spectrometry have been used more frequently owing to their accuracy and convenience. At the same time, some immunological methods, such as immunosensormethods, enzyme-linked immunosorbent assays (ELISA), immunofluorescence, etc. are also widely used.     

Unassisted eta2-coordination of polycyclic aromatic hydrocarbons to platinum(II)

The coordination of phenanthrene to the d8 Pt(II) center in (SP-4-2)-[Pt(C6F5)2(CO)(eta2-C14H10)] causes a slight pyramidalization at the metal-bound C atoms (C9 and C10), but no perceptible elongation of the corresponding C-C bond [C(13)-C(14) 132.0(5) vs. 133.8(5) pm in the free ligand].     

Oxidative-substitution reactions of polycyclic aromatic hydrocarbons with iodine(III) sulfonate reagents

Polycyclic aromatic hydrocarbons (PAH) undergo regioselective oxidative-substitution reactions with iodine(III) sulfonate reagents in dichloromethane to give the corresponding aryl sulfonate esters. The use of [hydroxy(tosyloxy)iodo]benzene in conjunction with trimethylsilyl isothiocyanate leads to thiocyanation of the PAH nucleus.     

Synthesis and characterization of solution-processable core-cyanated perylene-3,4;9,10-bis(dicarboximide) derivatives

Core-cyanated perylene-3,4;9,10-bis(carboxyimide) derivatives N-functionalized with tethered anthracenes (PDI3A-CN(2), PDI4A-CN(2)) and the corresponding solution-processable cycloadduct precursors (PDI3A-CA-CN(2), PDI4A-CA-CN(2)) were synthesized and their optical, electrochemical, and thermal properties characterized. These derivatives exhibit HOMO-LUMO energy gaps of ～2.1-2.3 eV and first reduction potentials between -50 and -150 mV versus SCE. The PDI3A-CN(2) and PDI4A-CN(2) cycloadducts are soluble in common organic solvents (>50 mg/mL), and the corresponding spin-coated films are converted to PDI3A-CN(2) and PDI4A-CN(2) films upon thermal annealing.     

Microhydration effects on the electronic spectra of protonated polycyclic aromatic hydrocarbons: [naphthalene-(H2O)(n = 1,2)]H+

Vibrational and electronic spectra of protonated naphthalene (NaphH(+)) microsolvated by one and two water molecules were obtained by photofragmentation spectroscopy. The IR spectrum of the monohydrated species is consistent with a structure with the proton located on the aromatic molecule, NaphH(+)-H(2)O. Similar to isolated NaphH(+), the first electronic transition of NaphH(+)-H(2)O (S(1)) occurs in the visible range near 500 nm. The doubly hydrated species lacks any absorption in the visible range (420-600 nm) but absorbs in the UV range, similar to neutral Naph. This observation is consistent with a structure, in which the proton is located on the water moiety, Naph-(H(2)O)(2)H(+). Ab initio calculations for [Naph-(H(2)O)(n)]H(+) confirm that the excess proton transfers from Naph to the solvent cluster upon attachment of the second water molecule.     

Palladium-catalyzed double cross-coupling reaction of 1,2-bis(pinacolatoboryl)alkenes and -arenes with 2,2′-dibromobiaryls: annulative approach to functionalized polycyclic aromatic hydrocarbons

This study demonstrates that the double cross-coupling reaction of 1,2-bis(pinacolatoboryl)alkenes and -arenes with 2,2′-dibromobiaryls proceeds smoothly with the aid of a catalytic amount of Pd(PPh₃)₄ in the presence of excess base to give a variety of polycyclic aromatic hydrocarbons, such as phenanthrenes, [5]helicene, dithienobenzenes, triphenylenes, dibenzo[g,p]chrysenes, and triphenyleno[1,2-b:4,3-b′]dithiophenes in good to high yields. It is noteworthy that the annulations using 2,2′-dibromooctafluorobiphenyl as an electrophile furnish the otherwise difficult to synthesize octafluorophenanthrenes and semi-fluorinated dibenzo[g,p]chrysenes in high yields.     

Determination of monohydroxylated metabolites of polycyclic aromatic hydrocarbons (OH-PAHs) from wastewater-treatment plants

A high-performance liquid chromatography separation coupled with mass spectrometry via an electrospray interface is proposed for the determination of the hydroxylated derivatives of polycyclic aromatic hydrocarbons (OH-PAHs) in treated and untreated wastewaters and suspended solids from sewage treatment plants (STPs). The developed SPE procedure was applied to spiked wastewater samples, with recovery yields (1000?mL; 100?ng?L^?1 spiking level) in the 65–87% (RSD: 6–12%) range for the selected OH-PAHs. The limits of detections ranged between 0.3 and 3.2?ng?L^?1, depending on the selected compound and on the investigated matrix. The proposed method was applied to the determination of the selected analytes in real samples from a sewage-treatment plant (STP). The investigated OH-PAHs were detected mainly in the particulate fraction. The exhibited mean concentrations of positive samples (as the sum of dissolved and particulate matter) in the STP final effluent ranged from 15 to 68?ng?L^?1.     

Synthesis and properties of aromatic polyamides derived from 2,6-bis(4-aminophenoxy)naphthalene and various aromatic dicarboxylic acids

2,6-Bis(4-aminophenoxy)naphthalene (2,6-BAPON) was synthesized in two steps from the condensation of 2,6-dihydroxynaphthalene with p-chloronitrobenzene in the presence of potassium carbonate, giving 2,6-bis(4-nitrophenoxy)naphthalene, followed by hydrazine hydrate/Pd—C reduction. A series of new polyamides were synthesized by the direct polycondensation of 2,6-BAPON with various aromatic dicarboxylic acids in the N-methyl-2-pyrrolidone (NMP) solution containing dissolved metal salts such as CaCl₂ or LiCl using triphenyl phosphite and pyridine as condensing agents. The polymers were obtained in quantitative yields with inherent viscosities of 0.62–2.50 dL/g. Most of the polymers were soluble in aprotic dipolar solvents such as N,N-dimethylacetamide (DMAc) and NMP, and they could be solution cast into transparent, flexible, and tough films. The casting films had yield strengths of 84–105 MPa, tensile strengths of 68–95 MPa, elongations at break of 8–36%, and tensile moduli of 1.4–2.1 GPa. The glass transition temperatures of the polyamides were in the range 155–225°C, and their 10% weight loss temperatures were above 505°C in nitrogen and above 474°C in air. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2147–2156, 1997     

Simultaneous microwave-assisted extraction of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, phthalate esters and nonylphenols in sediments

A new method was developed for the simultaneous extraction of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), phthalate esters (PEs), nonylphenols (NPs) and nonylphenol mono- and diethoxylates (NP1EOs and NP2EOs, respectively) in sediment samples by means of a closed microwave system. The extractions were carried out at 21 psi and 80% of microwave power and 15 ml of acetone were used as the common extraction solvent. The filtered extract was further fractionated in two groups using Florisil cartridges: PAHs and PCBs were eluted with n-hexane:toluene (4:1) and the PEs, NPs and ethoxylates were eluted with ethyl acetate. All the compounds were analysed by gas chromatography-mass spectrometry (GC-MS). In case of PAHs and PCBs, the developed method was validated by comparison of the results obtained for the certified reference material NIST 1944 with the certified values. In the absence of a reference material for phthalate esters and nonylphenols, one sediment sample was extracted twice under the optimal conditions in order to check than an exhaustive extraction of the analytes occurred. This method is currently used in the study of the distribution of those organic contaminants in the estuaries of the Bay of Biscay (Spain).     

Synthesis and lanthanide coordination properties of new 2,6-bis(N-tert-butylacetamide)pyridine and 2,6-bis(N-tert-butylacetamide)pyridine-N-oxide ligands

The compound 2,6-bis(N-tert-butylacetamide)pyridine (2) was obtained via a Ritter synthesis, and oxidation with oxone provided the title pyridine-N-oxide (3). The compounds were characterized by spectroscopic methods, and the molecular structure of the N-oxide was determined by single-crystal X-ray diffraction methods. The coordination chemistry with Eu(NO3)3 was examined by using 1:1 and 2:1 ligand/Eu ratios, and a single-crystal X-ray analysis for Eu(3)(NO3)3(H2O) was completed. The ligand 3 is found to chelate in a tridentate fashion on the Eu(III).