质谱法测定柴油中多环芳烃

采用气相色谱-质谱联用法测定柴油中多环芳烃,研究了固相萃取预处理样品影响因素和GC/MS气质联用数据处理最佳实验条件。通过对不同样品的重复性准确性试验,并与其它实验室进行数据比对,说明该方法的重复性好,准确度高。     

Polycyclic Aromatic Hydrocarbons from Candiota (South Brazilian) Coal Extracts

The bitumen composition of Candiota coal (south Brazil) was investigated. Coal bitumen was produced by Soxhlet extraction using toluene. Two chromatographic techniques were tested for bitumen fractionation: adsorption liquid chromatography on silica (ALCS) and adsorption liquid chromatography on alumina (ALCA). Results were compared in terms of the quality and quantity of hydrocarbons isolated. Several linear saturated hydrocarbons were found in the range of 14 to 33 carbons. Pyrene, chrysene, and other polycyclic hydrocarbons with recognized mutagenic and carcinogenic properties were found in the aromatic fractions. Chromatographic methodology using alumina shows better results in the fractionation of bitumen.     

Problems in the Extraction of Polycyclic Aromatic Hydrocarbons from Diesel Particulate Matter

In this work, a comparison between Soxhlet, ultrasonic, and microwave-assisted extraction (MAE) (using hexane:acetone 1:1) of polycyclic aromatic hydrocarbons (PAHs) from SRM 1650 diesel particulate matter was made. As good recoveries were not obtained for the higher molecular weight compounds, MAE with toluene and dichloromethane was also tested. Achieved recoveries were compared with the results obtained in the same assays made with SRM 1648 urban particulate matter and real atmospheric particulate samples. In order to explain the difficulty of the extraction of PAHs from SRM 1650 in comparison to SRM 1648 and real atmospheric particulate samples, elemental analysis, X-ray diffraction, and particle analysis using scanning electron microscopy coupled to an automatic computer imaging system were also made. It is important to notice that SRM 1650 shows a high percentage of carbon and differences in the morphology of the particles between SRM 1650 and SRM 1648 were observed.     

The Determination of Trace-Level PAHs and Diagnostic Ratios for Source Identification in Water Samples Using Solid-Phase Microextraction and GC/MS

The application of SPME-GC/MS for the determination of diagnostic ratios that can be used for spill identification was investigated in this study. The advantages of SPME include a solvent-free extraction, a high degree of selectivity, much shorter analysis time, and a small sample volume. The results obtained from 581 water samples were used to investigate the occurrence of alkyl-PAHs in these samples. Using the C 1 -dibenzothiophene and C 1 -phenanthrene ratio (C 1 -D/C 1 -P) of two single isomer peaks in each of these two different alkyl homologues, an alternative approach to hydrocarbon fingerprinting was developed. The results of source ratios that were determined on several ground water samples are discussed. The conclusion is made that the determination of the C 1 -D/C 1 -P source ratio in groundwater samples is useful, but is limited to samples containing these isomers in concentrations of >0.07 ng/cm 3 .     

Occurrence of Polycyclic Aromatic Hydrocarbons in Smoke Flavourings

The presence of Polycyclic Aromatic Hydrocarbons (PAHs) in four liquid smoke flavourings of different origins has been studied, in order to test whether a relation between their PAH content and their composition could be established, and to evaluate whether the use of these flavourings could involve a risk to human health. The samples were subjected to an alkaline treatment, extracted with cyclohexane, cleaned up, and the PAHs determined by gas chromatography-mass spectrometry. The results reveal a wide range of PAHs, especially in the commercial flavourings studied, which present higher concentrations of both total and carcinogenic PAHs than those obtained in the laboratory. Benzo(a)pyrene has been detected in three of the samples studied, but its levels do not exceed, in any of the cases, the 10 μg/kg value fixed by the FAO/WHO.     

Extraction of Polycyclic Aromatic Hydrocarbons in Barn Owls ( Tyto Alba ) from Northwest Spain by SFE and HPLC-FL Analysis

Supercritical fluid extraction (SFE) and high-performance liquid chromatography-fluorescence detection (HPLC-FL) were used to determine concentration of anthracene, benzo[ a ]anthracene, benzo[ a ]pyrene, benzo[ b ]fluoranthene, benzo[ ghi ]perylene, benzo[ k ]fluoranthene, chrysene, fluoranthene, pyrene, and indeno[1,2,3- cd ]pyrene in six classes of tissue (heart, liver, intestine, muscle, lung, and kidney) of 11 barn owls from Galicia (northwest Spain). We have detected fluoranthene and pyrene in >40.0% of samples, anthracene in 35.4%, and benzo[ a ]anthracene in 12.3%. Mean concentrations were between 0.398 w g/kg dry weight for anthracene and 4.855 w g/kg dry weight for fluoranthene. Lung and intestine tissues were more polluted than the other tissues.     

Recovery of Polycyclic Aromatic Hydrocarbons During Solvent Evaporation with a Rotary Evaporator

Analytical behavior of dichloromethane solutions containing polycyclic aromatic hydrocarbons (PAHs) was systematically studied through evaporation in a rotary evaporator. Starting sample concentration levels for each PAH were 0.167 w g/mL (concentrated) and 0.0167 w g/mL (diluted). Solvent reductions from 300 mL to final volumes of 30, 10, 3, and 1 mL (concentrated) and from 300 mL to 3 and 1 mL (diluted) were evaluated and each sample analyzed using gas chromatography-flame ionization detection (GC-FID). Factors affecting the percentage of analyte recovery include boiling point of analyte, the final sample volume, and starting sample concentration. When concentrated solutions were reduced from 300 mL to 1 mL, PAH recoveries were nearly all higher than 90%, except for naphthalene, acenaphthylene, and acenaphthene. However, when diluted solutions were evaporated to 1 mL, recoveries of all analytes dropped to 64.5% (naphthalene) ～ 89.2% (benzo[ ghi ]perylene). For evaporation to a final volume of 3 mL, recovery of PAHs in both concentrated and diluted solutions was higher than 90%. This implies that no significant losses of semivolatile analytes were found during evaporation of methylene chloride by rotary evaporation, regardless of boiling point or concentration level, until or unless the final volume was below 3 mL. Results of comparison of rotary evaporation and nitrogen blowdown showed that both concentration techniques provide qualitative recovery but rotary evaporation was more time effective.     

Photodegradation Products of Polycyclic Aromatic Hydrocarbons in Water and Their Amenability to Biodegradation

Saturated water solutions of anthracene, pyrene, benz[ a ]anthracene, and dibenz[ a,h ]anthracene were UV-irradiated in the presence of oxygen and their photodegradation products were identified. The products were then individually photolyzed. Several products of photolysis were identified chromatographically. Furthermore, the biodegradation of two photoproducts, 9,10-anthracenedione and benz[ a ]anthracene-7,12-dione, was studied separately and in the presence of the original polycyclic aromatic hydrocarbons (PAHs). The irradiation of anthracene first produced 9,10-anthracenedione and continuous illumination yielded additionally 1-hydroxy-9,10-anthracenedione, 1,4-dihydroxy-9,10-anthracenedione, 9-anthrone, and 1(3H)-isobenzofuranone. Photolysis of benz[ a ]anthracene produced benz[ a ]anthracene-7,12-dione and 1(3H)-isobenzofuranone. By irradiation of pyrene and dibenz[ a,h ]anthracene mainly diones of the original compounds were formed. In batch vial experiments, the biodegradation of 9,10-anthracenedione alone started with no lag phase whereas biodegradation of anthracene alone had a lag of 40 days. The lag for benz[ a ]anthracene biodegradation was, in the presence and absence of benz[ a ]anthracene-7,12-dione, 17 and 35 days, respectively.     

Surfactant Micellar Solutions as Alternative Solvents for Microwave-Assisted Extraction of Polycyclic Aromatic Hydrocarbons from a Spiked River Sediment

A procedure to extract polycyclic aromatic hydrocarbons (PAHs) from a contaminated river sediment is discussed; this combines short extraction times obtained by microwave energy with the peculiar solvent capability of aqueous micellar solutions. The technique, named microwave-assisted micellar extraction (MAME), was tested for the extraction of 11 PAHs from a spiked river sediment using polyoxyethylene (23) dodecyl ether (Brij 35), polyoxyethylene (10) dodecyl ether (C 12 E 10 ) or cetyl trimethylammonium bromide (CTAB). Different temperatures and extraction times were explored to establish whether this method has merit. Comparative measurements were made using sonication and Soxhlet extraction with acetone-hexane. Generally, Soxhlet extraction was revealed to be the most effective method to extract the PAHs from the solid matrix, with percent of recovery ranging from 92% to 102%. Nevertheless, high recoveries were also achieved by MAME using C 12 E 10 ; in fact, with only the exception of indeno[1,2,3- cd ]pyrene, the differences between recoveries obtained by MAME and Soxhlet extractions were below 10% for all the considered compounds.     

Determination of Semivolatile and Particulate Polycyclic Aromatic Hydrocarbons in SRM 1649a and PM 2.5 Samples by HPLC-Fluorescence

The concentrations of 15 "priority pollutant" semivolatile and particulate polycyclic aromatic hydrocarbons (PAHs) were determined in three sets of samples supplied by the National Institute for Standards and Technology (NIST) as part of an interlaboratory analytical exercise. The purpose of the exercise, organized by NIST and the U.S. Environmental Protection Agency, was to determine the comparability of measurements for various organic analytes among the participating laboratories, and to establish consensus values for SRM 1649a and interim materials. The commercially available SRM 1649a Atmospheric Urban Dust and two subsamples of this popular reference material were analyzed: an extract designated as Air Particulate Extract, and a resieved portion labeled Air Particulate I. The method used in our laboratory for the exercise consists of the extraction of the PAHs from the solid samples by ultrasonication, followed by separation and quantification using high-performance liquid chromatographyfluorescence detection. The accuracy and precision of the results obtained by our analytical protocol and by 14 other participating laboratories were evaluated using the International Union of Pure and Applied Chemistry guidelines of z-scores ( = 25% of the exercise assigned value) and p -scores. Using these guidelines the accuracy of our method provided results that are satisfactory for all 15 target PAHs (|z| h 2) determined in the Air Particulate Extract and, except for fluorene, in the Air Particulate I sample. Finally, application of the methodology is demonstrated for the quantification of PAHs present at the pg m m 3 range in PM 2.5 samples collected from 163 m 3 of air in the Los Angeles basin.     

Real-Time Monitoring of Polycyclic Aromatic Hydrocarbons in Cigarette Smoke Using Time-Resolved Laser-Induced Fluorescence

Cigarette smoke contains a large number of chemicals and gaseous compounds including polycyclic aromatic hydrocarbons (PAHs). Due to the importance of PAHs and their health effects in cigarettes, development of systems to analyze PAHs in cigarette smoke may become useful in developing a less harmful product. However, the complexity of cigarette smoke chemistry remains a significant obstacle in its analysis: many cigarette smoke components are produced due to reactions such as decomposition and recombination of cigarette components during the smoking process. Methods to analyze these reactions in real-time are needed. In this article the authors report direct monitoring of pyrene in mainstream smoke using time-gated laser-induced fluorescence (LIF) based on fiber optics. The time-gated detection system could provide a reduced background signal of mainstream smoke when using optimized gate delay and gate width parameters. The results demonstrate the feasibility of direct monitoring of PAHs in mainstream smoke.     

Spectrochemical Evaluation of Diisopropylamine as a Selective Fluorescence Quenching Agent of Polycyclic Aromatic Hydrocarbons in Acetonitrile

The ability of diisopropylamine to selectively quench the fluorescence intensity of nonalternant as opposed to alternant polycyclic aromatic hydrocarbons (PAHs) dissolved in acetonitrile was investigated. Sixteen alternant PAHs and 14 nonalternant PAHs were examined. Five PAHs, which contain a fixed double bond in the cyclopenta ring, were also included in this study. The experimental results indicated, with few exceptions, that diisopropylamine selectively quenched the fluorescence emission intensity of nonalternant PAHs, leaving the fluorescence intensity of most alternant PAHs unaffected. These results also confirmed the classification of the PAHs that contain a fixed double bond in the five membered rings as alternant not nonalternant PAHs. Limitations in the use of diisopropylamine as a selective quenching agent were also studied. Diisopropylamine does not retain its selective fluorescence quenching ability for nonalternant PAHs in acidic media.     

High-Molecular-Weight Polycyclic Aromatic Hydrocarbons in the Area and Vicinity of the Deza Chemical Plant,Czech Republic

Polycyclic aromatic hydrocarbons (PAHs) with molecular weight exceeding 278 amu were analyzed in air, water, and soils from the area and vicinity of the DEZA Chemical Plant (Vala w ské Mezi q í ) í, Czech Republic). Air and water were sampled using semipermeable membrane devices (SPMDs); grab sampling was applied for soils. Laser desorption/ionization-time-of-flight mass spectrometry (LDI-TOF MS) and liquid chromatography/ion trap mass spectrometry with atmospheric pressure chemical ionization (LC/APCI-ITMS) were employed for the quick assessment of PAH distribution and for the identification and quantification of some high-molecular-weight PAHs. Compounds with molecular mass up to 450 u were found. LDI-TOF mass spectra and selected LC/APCI-ITMS profiles (m/z 303, m/z 327, and m/z 351) were compared to identify potential source of contamination in this locality. High-molecular-weight PAHs were found in all environmental compartments in the area studied; their levels were quite high close to their source and decreased sharply with increasing distance from it.     

Ozonation of Polycyclic Aromatic Hydrocarbons in Water Solution

The degradation of three polycyclic aromatic hydrocarbons (PAHs): benzo[a]pyrene (BAP), chrysene (CHR), and fluorene (FLU) in aqueous solution using ozone was investigated. The influence of pH of the reaction mixture, ozone concentration, and the presence of a radical scavenger on the reaction rate was determined. The highest rate of PAHs disappearance was achieved in acidic solutions. The radical scavenger, tert-butanol, effectively inhibited the rate of PAHs destruction. The rate constants of direct reaction of PAHs with ozone were calculated and they were equal to (3.32 ± 0.21) × 10⁴; (1.10 ± 0.15) × 10⁴ and 44.8 ± 1.1 M^?1s^?1 for BAP, CHR, and FLU, respectively. The contributions of direct ozonolysis, and radical reaction to PAHs oxidation in ozonation processes, were evaluated.     

Partitioning of Polycyclic Aromatic Hydrocarbons in the Hair-Air System

Partitioning behavior of PAHs including NAP, FLO, PHE, and PYR was investigated. A plot of experimental K HA against log K OW gives a good linear relationship. A somewhat similar slope and intercept was obtained for the hair-air system using PCB values from the literature. In comparison to K VA values from the literature, lower values for K VA were obtained. This may be attributed from differences in species and degradability across biota groups. K HLA also exhibits good linear relationships with K OA and other physical chemical properties such as MW. The lipid fraction has a strong influence on bioconcentration in hair from the air and water. However, hair treatments, hair length, growth dilution, photodegradation, biodegradation, temperature, seasonal variations, wet and dry depositions could alter the degree of bioconcentration of PAHs in the hair.     

Formation and Lifetime of Polycyclic Aromatic Compounds During a National-Scale Transient Pollution Episode

Concentrations of selected particle-borne parent, alkylated, oxygenated, and nitrated polycyclic aromatic compounds (PACs) have been monitored before, during, and after a large national-scale wood-burning pollution episode (5 November 1994 and 4-5 November 1995). Toluene-modified supercritical CO 2 was used for the extraction of PACs from the collected particulate matter. Analysis was performed using an on-line multidimensional chromatographic technique using coupled liquid and gas chromatography (LC-GC) with loop interface. Comparison of average urban and wood smoke particulate PAC profiles identified a marked change in the ambient PAC profile for the pollution episode period, caused by the change in emission source from predominantly vehicular to wood smoke. A chemical mass balance model has been used to calculate the relative contributions from general urban and wood smoke PAC sources and from them, an estimation of the atmospheric life-time of the PAC emissions has been made. When monitored with 24 hr resolution in 1994, the concentrations of quinone-PAC oxidation products were found to peak 1 day after the maximum concentrations in the parent PAH were recorded, consistent with photochemically driven reactions with singlet state molecular oxygen. When concentrations were monitored on a more frequent basis in 1995, the concentrations of oxygenated species were seen to begin increasing in concentration before sunrise but still peaking after the maximum concentrations of parent PAH were recorded. The nighttime rise in product PAC suggests dark reactions with ozone or the NO 3 radical also may be occurring.     

Theoretical Examination of New Forms of Carbon Formed by Intra- or Intermolecular Dehydrogenation of Polycyclic Aromatic Hydrocarbons,Particularly Helicenes

Generalized helicenes are defined. A theoretical analysis is presented for the intramolecular dehydrogenation of helicenes, bridging adjacent rungs of the helix with the formation of 4-, 5-, and/or 6-membered rings, yielding helical tubulenes to which Euler's formula for polyhedra no longer applies as such constructions are derived from Möbius strips and correspond to nonplanar graphs (i.e., have crossing lines when drawn in two dimensions). Intermolecular dehydrogenation of two parallel-superimposed polycyclic aromatic hydrocarbons with formation of similar rings leads to convex polyhedral carbon cages. Carbon helical nanotubes and some carbon cages that are different from fullerenes are also discussed.     

The Use of Spectrofluorimetry for Monitoring the Bioaccumulation and the Biotransformation of Polycyclic Aromatic Hydrocarbons in Daphnia magna

A rapid and direct spectrofluorimetric method was tested in order to monitor the bioaccumulation of PAHs in Daphnia magna in a control media. After exposure to water containing benzo[ a ]pyrene or fluoranthene, daphnids were put in solvent, sonicated, and filtered. The fluorescence spectrum observed in the filtrate was recorded. Results were compared to HPLC measurements of the same pools of organisms. In fluoranthene experiments, the fluorescence peak of the daphnid extract spectrum was linearly related to the PAH content as measured with HPLC. In benzo[ a ]pyrene experiments, other fluorescent compounds progressively appeared in the sample. They were assumed to be metabolites. A linear regression involving fluorescence intensities at two different wavelengths was necessary for a satisfactory correlation with HPLC measurements. A water extraction was performed to isolate metabolites. None or very few fluoranthene metabolites were isolated in the aqueous phase, whereas increasing benzo[ a ]pyrene metabolites were observed while the exposure time increased.     

Interference of Soil Contaminants with Laccase Activity During the Transformation of Complex Mixtures of Polycyclic Aromatic Hydrocarbons in Liquid Media

The biotransformation of 16 polycyclic aromatic hydrocarbons (PAHs) in mixture was investigated in reactors in the presence of purified laccases of the fungus Pycnoporus cinnabarinus, ABTS as a redox mediator, 25% acetonitrile, and Tween 20. Several hydrocarbons from a synthetic mixture, such as anthracene and benzo[ a ]pyrene, were converted up to 80% into quinones, whereas others also belonging to three- and five-ring chemicals were less transformed. Chrysene and benzo[ k ]fluoranthene were not oxidized by the laccase mediator system. Moreover, hydrocarbons extracted from an industrial soil were all recalcitrant to enzymatic attack. This lack of reactivity of the laccases toward the hydrocarbons could be due to the presence of interfering compounds coextracted from the soil, such as metals.