Extraction, polycyclic aromatic

Pressurised hot water extraction has been used to isolate polycyclic aromatic hydrocarbons from soil [104,105]. Ramos et al. [106] reported an rapid (ten minutes) miniaturised pressurised liquid extraction method using only 100 pi solvent for extracting polycyclic aromatic hydrocarbons from soil. 

Microwave-assisted extractions (MAE) can be performed in open (focused MAE) or closed (pressurized MAE) flasks. This technique is commonly used for extractions from complex and difficult sample matrices, replacing time- and solvent-intensive Soxhlet extractions or hydrodistillations.46 MAE is also widely applied to environmental samples, for example, for extracting polycyclic aromatic hydrocarbons (PAH) from soil, methylmercury from sediments, and trace metals and pesticide residues from plant material47 48 The use of microwave treatment instead of hydrodistillation offers a solvent-free separation technique essential oils are heated and dry-distilled 46... 

However, Popp et al. [148] desorbed extracted polycyclic aromatic hydrocarbons by ultrasonic treatment of the stir bar in acetonitrile or acetonitrile water mixtures in order to perform liquid chromatographic analyses of the extract. 

Figure 12 Level of extractable polycyclic aromatic hydrocarbons with depth.

The ability of several methods to extract polycyclic aromatic hydrocarbons (PAHs) and other petroleum hydrocarbons from marine sediments was examined. Comparisons of soxh-let and methylene chloride reflux methods gave extraction efficiencies that showed no statistical difference in the return of PAHs however, the return when using ball-mill tumbling was significantly lower. The relative content of individual parent PAH compounds, parent compound distributions (PCDs), and alkyl homologue distributions (AHDs) of PAHs was calculated using capillary column GC-MS. The similarities of the distributions showed that any of the three methods could have been used to calculate these distributions. An examination of several extraction methods commonly used for the extraction of petroleum hydrocarbon material from sediment samples showed differences in results that depended on the extraction method employed. In addition, the methods varied in their ability to extract resolved versus unresolved material and to return aliphatic and aromatic hydrocarbon compounds. 

Hexagonally ordered silica, SBA-15, were also fabricated with PANI to prepare PANI/hexagonally ordered silica nanocomposite, which was used to extract polycyclic aromatic hydrocarbons from aqueous solutions, including naphthalenes, biphenyl, acenaphthene, anthracene, pyrene, and so on [37]. The same nanocomposite exhibited selective adsorption toward 2,4-dini-trophenol in aqueous solution in the presence of phenol with the adsorption capacity of 55.0 mg/g [38]. Chemical oxidation of aniline on hexagonal mesoporous silica (HMS) was carried out to generate PANI/HMS nanocomposite for Ni(II) elimination from aqueous solutions [39]. This process was spontaneous and endothermic and can be applied to Freimdlich isotherm and a pseudo-second-order kinetic. The removal efficiency was 99.87% for 50 mg/L Ni(II) solution, and the maximum sorption capacity can reach 253.17 mg/g at 300 mg/L Ni(II) solution. 2,6-Dichlorophenol can be selective removed from aquatic environment by PANI/silica gel composite [40]. A spontaneous and endothermic process was also observed with a Langmuir isotherm. 

Although the requirement for specialized high pressure equipment has limited its application, extraction with supercritical carbon dioxide maintained at temperatures and pressures above the critical point where separate liquid and vapor phases do not exist is a very effective means of extracting some organic analytes. Method 3561 is used to extract polycyclic aromatic hydrocarbons such as acenaphthene, benzo(a)py-rene, fluorene, and pyrene from solid samples using a relatively complicated three-step procedure. 

The performance of microwave-assisted decomposition of most difficult samples of organic and inorganic natures in combination with the microwave-assisted solution preconcentration is illustrated by sample preparation of carbon-containing matrices followed by atomic spectroscopy determination of noble metals. Microwave-assisted extraction of most dangerous contaminants, in particular, pesticides and polycyclic aromatic hydrocarbons, from soils have been developed and successfully used in combination with polarization fluoroimmunoassay (FPIA) and fluorescence detection. 

ACID-BASED SURFACTANT CLOUD POINT EXTRACTION AND PRECONCENTRATION OF POLYCYCLIC AROMATIC HYDROCARBONS PRIOR TO FLUORESCENCE DETERMINATION... 

Zebiihr et al. (29) developed an automated system for determining PAHs, PCBs and PCDD/Fs by using an aminopropyl silica column coupled to a porous graphitic carbon column. This method gives five fractions, i.e. aliphatic and monoaromatic hydrocarbons, polycyclic aromatic hydrocarbons, PCBs with two or more ortho-chlorines, mono-ort/io PCBs, and non-ortho PCBs and PCDD/Fs. This method employed five switching valves and was successfully used with extracts of sediments, biological samples and electrostatic filter precipitates. 

One example of normal-phase liquid chromatography coupled to gas chromatography is the determination of alkylated, oxygenated and nitrated polycyclic aromatic compounds (PACs) in urban air particulate extracts (97). Since such extracts are very complex, LC-GC is the best possible separation technique. A quartz microfibre filter retains the particulate material and supercritical fluid extraction (SPE) with CO2 and a toluene modifier extracts the organic components from the dust particles. The final extract is then dissolved in -hexane and analysed by NPLC. The transfer at 100 p.1 min of different fractions to the GC system by an on-column interface enabled many PACs to be detected by an ion-trap detector. A flame ionization detector (PID) and a 350 p.1 loop interface was used to quantify the identified compounds. The experimental conditions employed are shown in Table 13.2. 

KAYALI-SAYADI M N, RUBIO-BARROSO S, CUESTA-JIMENEZ M P and PALO-DIEZ L M (1998) Rapid determination of polycyclic aromatic hydrocarbons in tea infusion samples by high-performance liquid chromatography and fluorimetric detection based on solid-phase extraction , 123, 2145-8. 

Nishioka MG, CC Howard, DA Conros, LM Ball (1988) Detection of hydroxylated nitro aromatic and hydroxy-lated nitro polycyclic aromatic compounds in ambient air particulate extract using bioassay-directed fractionation. Environ Sci Technol 22 908-915. 

Jacob J, and Grimmer G (1994) Extractability of polycyclic aromatic hydrocarbons from environmental matrices. Quimica Analitica 13 (Suppl.i) ii9-i23. 

May WE, and Wise SA (1984) Liquid chromatographic determination of polycyclic aromatic hydrocarbons in air particulate extracts. Anal Ghem 56 225-232. 

Reza, J., Trejo, A., Vera-Avila, L.E. (2002) Determination of the temperature dependence of water solubilities of polycyclic aromatic hydrocarbons by a generator column-on-line solid-phase extraction-liquid chromatographic method. Chemosphere 47, 933-945. 

Berset JD, Ejem M, Holzer R, Lischer P (1999) Comparison of different drying, extraction and detection techniques for the determination of priority polycyclic aromatic hydrocarbons in background contaminated soil samples. Anal Chim Acta 383(3) 263-275... 

Ratola N, Lacorte S, Alves A et al (2006) Analysis of polycyclic aromatic hydrocarbons in pine needles by gas chromatography-mass spectrometry. Comparison of different extraction and clean-up procedures. J Chromatogr A 1114 198-204... 

Procedure 12.5 illustrates the use of sonication in extraction procedures. It has been used in the extraction of phenols, amines, and polycyclic aromatic hydrocarbons. It has also been used to extract hydrocarbons from clay soils [8,9,17],... 

Sanchez-Brunete C, Miguel E, Tadeo J. Rapid method for the determination of polycyclic aromatic hydrocarbons in agricultural soils by sonication-assisted extraction in small columns. J. Sep. Sci. 2006 29 2166-2172. 

Miege C, Dugay J, Hennion MC. Optimization, validation and comparison of various extraction techniques for the trace determination of polycyclic aromatic hydrocarbons in sewage sludges by liquid chromatography coupled to diode-array and fluorescence detection. J. Chromatogr. A 2003 995 87-97. 

A gaseous sample is passed through a solid material, such as silica gel or polyurethane foam (PUF), in a tube. A glass fiber filter is often put in front of the solid support to capture particle-phase constituents, while the vapor-phase compounds are captured on the solid support. This is used for semivolatile analytes, such as polycyclic aromatic hydrocarbons and pesticides. The solid support is then usually extracted in the lab with a solvent (see techniques described later in this chapter), and then the techniques used for liquid samples are followed. 

The carcinogenicity of polycyclic aromatic compound-rich tyre extender oils has lead to the proposal of a legislative ban on their use in Europe. The suitability of naphthenic oils as non-toxic plasticisers in tyre treads is discussed and results are presented of experimental studies of the use of these plasticisers in SBR, EPDM, sulphur-cured EPDM and peroxide-cured EPDM. Despite their low aromatic content, the naphthenic plasticisers are shown to give good results in SBR, probably as a result of the contribution to solvent characteristics of the naphthenic molecular structure. The use of naphthenic oils is expected to increase worldwide as they are said to be one of the best alternatives to aromatic extracts with regard to solvent properties, compatibility, performance and availability. 

Accelerated solvent extraction is a new technique for the extraction of a range of organic pollutants from soils and related material. The technique is based on the use of a solvent or combination of solvents to extract organic pollutants at elevated pressure and temperature from a solid matrix. The range of organic pollutants for which the technique is proposed includes semivolatile compounds, organochlorine pesticides, organophosphorus pesticides, chlorinated herbicides, polychlorinated biphenyls and polycyclic aromatic hydrocarbons [53-56],... 

Robbat et al. [42] carried out on-site detection of polycyclic aromatic hydrocarbons in hexane extract of sediments using thermal desorption gas chromatography-mass spectrometry. 

M.A. Lage Yusti and J.L. Cortizo Davina, Supercritical fluid extraction and high-performance hquid chromatography-fluorescence detection method for polycyclic aromatic hydrocarbons investigation in vegetable oil. Food Cont. 16 (2005) 59-64. 

---