Development of a focused ultrasonic-assisted extraction of polycyclic aromatic hydrocarbons in marine sediment and mussel samples

Focused ultrasonic-assisted extraction (FUSE) is a new and particular technique based on the cavitation effect. In this work, the focused ultrasound assisted extraction was studied and developed for the extraction of polycyclic aromatic hydrocarbons from marine sediments and mussel tissues. The variables influencing the extraction (amplitude of the ultrasound pulse, the extraction time and the solvent) were studied by a full factorial design and a central composite design. As a result, flat response surfaces were obtained and the most convenient conditions were 45% of ultrasound amplitude, 120 s of extraction time and 5 mL of acetone. Both accuracy and precision of the method were evaluated by means of two certified reference materials (marine sediment and mussel tissue) and the results were also compared to those obtained by microwave assisted extraction.     

Semi-fused hexaphenyl hexa-peri-hexabenzocoronene: a novel fluorophore from an intramolecular Scholl reaction

A semi-fused hexaphenyl hexabenzocoronene derivative (hexaphenyl-1/2HBC) was discovered and isolated from an intramolecular Scholl reaction of an oligo(ethyleneglycol) substituted hexabiphenylbenzene. This new derivative exhibits blue-shifted λ_em and significantly enhanced fluorescence in dichloromethane compared to the completely cyclized hexaphenyl-HBC derivative.     

Characterization of Supercomplex Crude Oil Mixtures: What Is Really in There?

Through different windows : One major obstacle in energy research is the complexity and variety of compounds present in crude oil. A study of different ionization methods for mass spectrometry shows that the mass spectrum very strongly depends on which method is used.

     

Spatial trends of petroleum hydrocarbons in water and sediments

Seasonal changes in petroleum hydrocarbons in water and streambed sediment from selected oil-related areas of Ondo State, Nigeria have been examined using gravimetric and infrared methods. The highest and lowest total petroleum hydrocarbon concentrations (TPH) in water (sediments in brackets) gravimetrically were 3.49 mg L⁻¹ (199.3) mg kg⁻¹ and 0.003 mg L⁻¹ (81.0) mg kg⁻¹ while the concentrations found by IR were 24.0 mg L⁻¹ (135.0 mg kg⁻¹) and 14.0 mg L⁻¹ (33.0 mg kg⁻¹) respectively. The two seasons were positively correlated (α = 0.01) by both methods. The TPH level was well correlated with the sediment organic carbon (OC) during both seasons. The characteristic carbonyl (C=O) vibrations at 1650 cm⁻¹ and 1700 cm⁻¹ indicate oxidation of the oil residue. The study recommends further investigation into the type of organics present to evaluate their toxicity and appropriate remediation.      

Multiwalled carbon nanotubes/cryogel composite, a new sorbent for determination of trace polycyclic aromatic hydrocarbons

A new cost-effective sorbent, multiwalled carbon nanotubes/poly (vinyl alcohol) cryogel composite (MWCNTs/PVA), was prepared under frozen conditions for the extraction and preconcentration of trace polycyclic aromatic hydrocarbons (PAHs) in water samples. This was followed by high performance liquid chromatography (HPLC) with fluorescence detection. The proposed method provided a high enrichment factor with an extremely high extraction efficiency (89–98%) of three spiked levels of three standard PAHs with relative standard deviations of less than 8%. The low detection limits of the method were 5, 8 and 5 ng L^{− 1} for benzo(a)anthracene, benzo(b)fluoranthene and benzo(a)pyrene, respectively. This method was successfully applied for the determination of the three PAHs in real water samples where they were found in the range of 7 to 22 ng L^{− 1}. The major advantages of MWCNTs/PVA over the commercial C₁₈ is that it can be operated at a higher loading flow rate without sorbent clogging and requires a shorter time for completion without any loss of extraction efficiency.     

Direct determination of benzo[a]pyrene in water samples by a gold nanoparticle-based solid phase extraction method and laser-excited time-resolved Shpol'skii spectrometry

The strong affinity between polycyclic aromatic hydrocarbons (PAH) and the surface of gold colloids is investigated to device an extraction method for water samples. Within the 20-100 nm particle diameter range, the 20 nm gold nanoparticles showed the best extraction efficiencies for all the studied analytes. The new approach is combined to laser-excited time-resolved Shpol'skii spectrometry for the direct analysis of benzo[a]pyrene in drinking water samples. For a 500 μL sample volume, the analytical figures of merit demonstrate precise and accurate analysis at the parts-per-trillion level. The extraction efficiencies are statistically equivalent to 100% with relative standard deviations lower than 2%. The average recoveries were varied from 87.5% to 96.5% for different concentration of analytes. The simplicity of the experimental procedure, the low analysis cost, and the excellent analytical figures of merit demonstrate the potential of this approach for routine analysis of drinking water samples.     

Reduction of polycyclic aromatic hydrocarbons promoted by cobalt or manganese nanoparticles

A new methodology for the partial reduction of polycyclic aromatic and heteroaromatic hydrocarbons under mild reaction conditions is presented, the process being a reasonable alternative to the catalytic hydrogenation or the Birch reaction. The reduction protocol described is based on the use of cobalt or manganese nanoparticles generated in situ in a simple and economic way, by reduction of commercially available CoCl₂·6H₂O or MnCl₂·2H₂O in the presence of lithium sand and the corresponding PAH, acting itself as an electron carrier. The use of a deuterium-oxide-containing cobalt(II) salt allows the simple preparation of deuterium labeled products. The regiochemistry and degree of reduction in the case of 1-substituted naphthalene derivatives markedly depends on the nature of the metal-NPs used.     

工作场所空气中54种挥发性烃类物质的检测

采用Tenax-TA吸附剂管采集工作场所空气中54种挥发性烃类化合物,经热脱附-气相色谱检测。结果显示,1,1-二氯乙烯、二氯甲烷、1,2-二氯乙烯(反式)、1,2-二氯乙烯(顺式)、2,2-二氯丙烷、溴氯甲烷、1,1,1-三氯乙烷、1,2-二氯乙烷、1,1-二氯丙烯的相关系数在0.9941～0.9986之间,溴氯甲烷、二溴甲烷、三氯甲烷、溴二氯甲烷、2,2-二氯丙烷、二溴氯甲烷、溴仿的检出限为5.4～10.3ng,最低检出浓度0.01～0.1mg/m3(采样体积0.5L)。其余38种挥发性烃类物质的相关系数均大于0.999,最低检出浓度0.001～0.01mg/m3;其中烯烃类检出限为0.4～2.7ng、烷烃类为1.4～3.7ng、芳香烃类为0.2～1.0ng、萘为2.2ng;54种挥发性烃类物质的热脱附效率92.1%～113.1%,RSD为0.6%～17.4%,除1,2-二氯乙烯(顺式)、1,1-二氯乙烷、1,1,1-三氯乙烷、1,1-二氯乙烯、2,2-二氯丙烷、三氯甲烷、1,2-二氯乙烯(反式)、二氯甲烷、溴氯甲烷的RSD值在5.1%～17.4%外,其余45种挥发性烃类物质的RSD均小于5%;9种化合物...     

Ultrasonication extraction and gel permeation chromatography clean-up for the determination of polycyclic aromatic hydrocarbons in edible oil by an isotope dilution gas chromatography–mass spectrometry

An analytical method for the determination of US EPA priority pollutant 16 polycyclic aromatic hydrocarbons (PAHs) in edible oil was developed by an isotope dilution gas chromatography–mass spectrometry (GC–MS). Extraction was performed with ultrasonication mode using acetonitrile as solvent, and subsequent clean-up was applied using narrow gel permeation chromatographic column. Three deuterated PAHs surrogate standards were used as internal standards for quantification and analytical quality control. The limits of quantification (LOQs) were globally below 0.5 ng/g, the recoveries were in the range of 81–96%, and the relative standard deviations (RSDs) were lower than 20%. Further trueness assessment of the method was also verified through participation in international cocoa butter proficiency test (T0638) organised by the FAPAS with excellent results in 2008. The results obtained with the described method were satisfying (z ≤ 2). The method has been applied to determine PAH in real edible oil samples.     

First identification of benzo[cd]phenanthro[1,2,3-lm]perylene by high-pressure liquid chromatography with ultraviolet-visible spectroscopy and mass spectrometry

Benzo[cd]phenanthro[1,2,3-lm]perylene has been identified as a product of supercritical 1-methylnaphthalene pyrolysis from an experiment performed at 585 °C, 110 atm, and 140 s in a supercritical fluid flow reactor. The identification of benzo[cd]phenanthro[1,2,3-lm]perylene is based on the product's mass spectrum, HPLC elution time, and UV absorbance spectrum. The mass spectrum of the identified 1-methylnaphthalene pyrolysis product, called component I here, reveals a molecular weight of 426, corresponding to a C₃₄H₁₈ polycyclic aromatic hydrocarbon (PAH). The extremely long HPLC elution time, 20–48 min longer than those of the four other C₃₄H₁₈ PAH components in this product mixture, indicates that component I has a planar structure with a high length-to-breadth ratio. Annellation theory is used to interpret and compare the UV spectrum of component I with those of the C₃₀H₁₆ benzo[cd]naphtho[1,2,3-lm]perylene and the C₃₆H₁₈ teropyrene, structures with one ring less and one ring more, respectively, than that of component I. This analysis of component I's UV spectrum, in conjunction with its mass spectrum and HPLC elution behavior, all lead to the identification of component I as the nine-ring PAH benzo[cd]phenanthro[1,2,3-lm] perylene, a molecule whose existence has never before been documented.