天然生育酚中痕量多环芳烃脱除工艺的研究

采用活性炭吸附法脱除天然生育酚中的多环芳烃（PAHs）,考察了脱除溶剂、活性炭种类、搅拌时间、温度、活性炭用量、脱除次数对多环芳烃脱除率的影响。结果表明,用乙醇（分析纯）溶剂溶解生育酚（液固比为5：1）,加入10％的HC-2型活性炭,在20℃下搅拌45min,对PAHs可以达到较好的脱除效果（对轻PAHs的脱除率达到48％以上,对重PAHs的脱除率达到98％以上,对总PAHs的脱除率达到88％以上）,重PAHs的残留量为5．22ng／g,轻PAHs的残留量为86．22ng／g。     

Mechanisms of the aqueous photodegradation of polycyclic aromatic hydrocarbons

The role of O2 and photoionization as well as the involvement of polycyclic aromatic hydrocarbon (PAH) cation radicals (P+) in the photodegradation of nine PAHs was examined. Photodegradation quantum yields for all PAHs increased with increasing O2 concentration, illustrating the key role of O2 in the photodegradation mechanism. In the presence of a series of electron donors (to P+), the photodegradation rate constants of most PAHs were largely unaffected at low O2 concentrations (< or = 250 microM), indicating that P+ is not extensively produced. However, at higher O2 concentrations (up to 1.2 mM), the presence of the donors substantially lowered photodegradation rates for most PAHs, indicating that P+ is produced and is arising from O2 reaction with the excited singlet state. Because little P+ was detected at low O2 concentrations and, further, because degradation rates were not enhanced in the presence of N2O, we conclude that photoionization is unimportant. With some exceptions, photodegradation can proceed through reaction of O2 with both excited singlet and triplet states of the PAHs. Our results indicate that photodegradation via the excited singlet state occurs primarily through electron transfer to O2, whereas degradation via the triplet occurs predominately through a direct reaction of O2 with the PAH within the collision complex.     

食品中多环芳烃及卤代多环芳烃的研究进展

综述了多环芳烃及卤代多环芳烃的性质、毒性及国内外食品中的污染情况和研究现状,并对目前的分析测定方法进行了介绍,希望为我国开展食品领域内多环芳烃和卤代多环芳烃的研究提供参考。     

Reaction of polycyclic aromatic hydrocarbons adsorbed on silica in aqueous chlorine

The reaction of polycyclic aromatic hydrocarbons (PAHs) previously adsorbed on silica gel or diatomaceous earth with sodium hypochlorite was carried out to elucidate their reactivity to aqueous chlorine. It was demonstrated that the PAHs adsorbed on silica reacted more rapidly than the PAHs themselves in water, leading to the formation of many chlorinated and oxidized derivatives. A similar reaction in the presence of potassium bromide was found to preferentially produce corresponding brominated derivatives. These reactions seem to proceed through PAHs adsorbed on the silica surface and halogenating agents, the electrophilicity of which may be raised by the catalytic effect of the silanol group of the silica surface. These findings from the environmental viewpoint suggest that the reaction of hydrophobic compounds adsorbed on sediment cannot be neglected.     

天然生育酚中多环芳烃的脱除方法

多环芳烃是天然生育酚中普遍存在的一种化合物,它是由含有两个及两个以上苯环稠和而成.此类化合物对生物及人类的毒害主要是参与机体的代谢过程,因具有强烈的致癌性、致畸性、致突变性而受到严格限制,目前欧美各国的法规都对生育酚中的多环芳烃采取了近乎苛刻的要求,国内有许多相关生产厂家,因为无法突破此道技术难关,而无法参与欧美市场,因此,寻找到一种既经济又简易可行的脱除方法,是天然生育酚工业化生产中必须要解决的问题,同时也是为人类健康作出必要的保证.本文就当前主要的几家天然生育酚生产商的多环芳烃脱除方法进行了总结与评述,并对比较常用的液液萃取法、吸附剂吸附法、柱层析法和复合脱除法的工业化可行性进行了简要的评价.     

Removal of polycyclic aromatic hydrocarbons from contaminated soil by aqueous DNA solution

An aqueous DNA solution was applied for the extraction of polycyclic aromatic hydrocarbons (PAHs) from a spiked soil. Solubilities of 0.56, 11.78, and 11.24 mg L(-1) for anthracene, phenanthrene, and pyrene, respectively, were achieved after 1 day equilibration in 1% DNA. Using a spiked soil that contained 72 mg kg(-1) anthracene, 102 mg kg(-1) phenanthrene, and 99 mg kg(-1) pyrene, extractions of close to 88, 78, and 94%, respectively, were attained with 5% DNA at a 1:50 soil/extractant ratio. Maximum PAH dissolution occurred after 4-6 h. Comparative tests showed the main advantage of DNA over methyl-beta- and gamma-cyclodextrins and Tween 80 for pyrene removal. An ionic strength of 0.1 M NaCl was found necessary for maximum PAH dissolution and extraction. The performance of hexane regenerated DNA also remained stable after three stages of recycling. These results show the huge potential of DNA as an aqueous washing agent for PAH-contaminated soil.     

Aqueous photodegradation of polycyclic aromatic hydrocarbons

Photodegradation of 12 polycyclic aromatic hydrocarbons was studied in aerated pure water, solutions of Suwannee River fulvic acid, and natural waters using polychromatic light (>290 nm). Quantum yields in pure water varied from 3.2 x 10(-5) to 9.2 x 10(-3). No obvious relationships were evident among the quantum yields and molecular properties. Photodegradation rate constants in solutions of Suwannee River fulvic acid or natural waters were largely unchanged compared to rate constants in pure water. Estimates of PAH photodegradation rates in natural waters can thus be obtained employing the quantum yields in pure water, PAH absorption, and solar irradiance. Calculated rate constants for photodegradation in surface waters during the summertime at mid-latitude varied from 3.2 x 10(-3) to 7.6 h(-1).     

Emission of polycyclic aromatic hydrocarbons in China

Emission of 16 polycyclic aromatic hydrocarbons (PAHs) listed as U.S. Environmental Protection Agency (U.S. EPA) priority pollutants from major sources in China were compiled. Geographical distribution and temporal change of the PAH emission, as well as emission profiles, are discussed. It was estimated that the total PAH emission in China was 25,300 tons in 2003. The emission profile featured a relatively higher portion of high molecular weight (HMW) species with carcinogenic potential due to large contributions of domestic coal and coking industry. Among various sources, biomass burning, domestic coal combustion, and coking industry contributed 60%, 20%, and 16% of the total emission, respectively. Total emission, emission density, emission intensity, and emission per capita showed geographical variations. In general, the southeastern provinces were characterized by higher emission density, while those in western and northern China featured higher emission intensity and population-normalized emission. Although energy consumption in China went up continuously during the past two decades, annual emission of PAHs fluctuated depending on the amount of domestic coal consumption, coke production, and the efficiency of energy utilization.     

A novel cloud-point extraction process for preconcentrating selected polycyclic aromatic hydrocarbons in aqueous solution

A novel but simple cloud-point extraction (CPE) process is developed to preconcentrate the trace of selected polycyclic aromatic hydrocarbons (PAHs) with the use of the readily biodegradable nonionic surfactant Tergitol 15-S-7 as extractant. The concentrations of PAHs, mixtures of naphthalene and phenanthrene as well as pyrene, in the spiked samples were determined with the new CPE process at ambient temperature (23 degrees C) followed by high performance liquid chromatography(HPLC) with fluorescence detection. More than 80% of phenanthrene and pyrene, respectively, and 96% of naphthalene initially present in the aqueous solutions with concentrations near or below their aqueous solubilities were recovered using this new CPE process. Importantly Tergitol 15-S-7 does not give any fluorometric signal to interfere with fluorescence detection of PAHs in the UV range. No special washing step is, thus, required to remove surfactant before HPLC analyses. Different experimental conditions were studied. The optimum conditions for the preconcentration and determination of these selected PAHs at ambient temperature have been established as the following: (1) 3 wt% surfactant; (2) addition of 0.5 M Na2SO4; (3) 10 min for equilibration time; and (4) 3000 rpm for centrifugal speed with duration of 10 min.     

Enhanced sorption of polycyclic aromatic hydrocarbons to tetra-alkyl ammonium modified smectites via cation-pi interactions

The objective of this study was to characterize molecular sorptive interactions of polycyclic aromatic hydrocarbons (PAHs) by organoclays modified with quaternary ammonium cations. Three PAHs, naphthalene (NAPH), phenanthrene (PHEN), and pyrene (PYR), and three chlorobenzenes, 1,2-dichlorobenzene (DCB), 1,2,4,5-tetrachlorobenzene (TeCB), and pentachlorobenzene (PtCB), were sorbed from aqueous solution to reference montmorillonite clays (SWy-2) exchanged respectively with tetramethyl ammonium (TMA), tetraethyl ammonium (TEA), tetra-n-butyl ammonium (TBA), and hexadecyltrimethyl ammonium (HDTMA) cations. Solute hydrophobicities are compared between PAHs and chlorobenzenes using the solute n-octanol-water partition coefficient, n-hexadecane-water partition coefficient, and polyethylene-water distribution coefficient. The PAHs show several- to more than 10-fold greater sorption than the chlorobenzenes having close hydrophobicities but fewer delocalized pi electrons (NAPH/DCB, PHEN/TeCB, and PYR/ PtCB) by TEA-, TBA-, and HDTMA-clays. Furthermore, the PAHs show greater trends of solubility enhancement than the compared chlorobenzenes by TMA, TEA, and TBA in aqueous solution. The enhanced sorption and aqueous solubility of PAHs are best described by cation-pi interactions between ammonium cations and PAHs relative to chlorobenzenes that are incapable of such interactions. Cation-pi complexation between PAHs and tetra-alkyl ammonium cations in chloroform was verified by ring-current-induced upfield chemical shifts of the alkyl groups of cations in the 1H NMR spectrum.     

Occurrence of polycyclic aromatic hydrocarbons in smoked cheese

The presence of polycyclic aromatic hydrocarbons (PAH) in smoked cheeses of different origin was studied. The samples were subjected to an initial extraction of fat and an alkaline treatment, extracted with cyclohexane, cleaned up by means of solid-phase extraction tubes, and analyzed by gas chromatography/mass spectrometry (GC/MS) operating in selective ion-monitoring mode (SIM). The results revealed the presence of numerous polycyclic aromatic hydrocarbons in the exterior zone of the samples, some of them with methyl groups. In all cases, the concentrations of compounds of low molecular weight were much higher than those of high molecular weight. Polycyclic aromatic hydrocarbons with varying degrees of carcinogenicity were identified, including benzo(a)pyrene in concentrations, which, although they did not exceed the limit established for this compound in the rind of ripened cheeses, do exceed the limit of 0.03 microg/kg fixed for other foods smoked with smoke flavorings. Significant differences in the number and concentration of PAH in smoked cheese also were observed from rind to interior, the rind being the most contaminated zone.     

食用油中多环芳烃的研究进展

多环芳烃(PAHs)是指2个或2个以上苯环以稠环形式相连的一类化合物,具有基因毒性和致癌性.对食用油中PAHs的来源、检测方法及控制和脱除方法进行了详尽的阐述,并指出PAHs前处理方法和控制、脱除方法是未来的研究方向.     

高脂食品中多环芳烃研究

多环芳烃具有非极性强特点,易在脂质含量丰富食品中造成污染。该文对富脂肉类等高脂肪食品中多环芳烃来源、形成及污染现状、检测方法等进行概述,并对控制其中多环芳烃污染方法进行总结和讨论。     

烟熏肉制品中多环芳烃的提取及检测分析

烟熏肉制品作为肉类加工制品的一大类,由于其独特的风味深受广大消费者的欢迎。但是,在烟熏肉中含有致癌的多环芳烃(PAHs),影响着人们的健康。主要从烟熏肉制品中多环芳烃(PAHs)的提取、检测方法对其进行综述,以实现多环芳烃的快速检测和达到寻找控制多环芳烃方法的目的。