Extraction efficiencies several PAHs

It is important to note that several works, in both environmental and food analysis, compare the extraction performance of the IL-based surfactant with the conventional cationic surfactant CTAB [20, 36, 56, 60, 61]. For example, Pino et al. have reported much better extraction efficiencies of PAHs from marine sediments when using Cj C Im-Br (being quantitative) than when using CTAB under the same extraction conditions [36], Moreover, this application was validated using a certified reference material (CRM). 

Table II. Extraction Efficiencies (%) for Several PAHs using Cyclodextrin-Modified Extraction...

The utility of CDx solvent extraction for separating mixtures was evaluated by measuring the individual extraction efficiencies of the components in several binary PAH mixtures. The results of these mixture analyses are shown in Table III. 

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. 

As shown in several studies, the pressure is usually a minor variable for the resulting efficiency in PHSE [18-20] provided the level used is high enough to maintain the solvent in the liquid state. In a study by Saim et al. [20], the total amount of PAHs extracted at different pressures (85 and 165 bar) with all other variables kept constant (120°C and 9 min static extraction) was similar (differences were within experimental error). In some cases, however, pressure can be a key to ensuring complete analyte removal. The use of high pressures facilitates extraction from samples where the analytes have been trapped in matrix pores. The pressure increment forces the solvent into areas of the matrices that would not normally be contacted by them under atmospheric conditions. For example, if analytes are trapped in pores, and water (or even an air bubble for small pores) has sealed pore entrances, then organic solvents may not be able to contact such analytes and extract them. The pressure increase (along with elevated temperatures and reduced solvent surface tensions) forces the solvent into the pore to contact the analytes. 

Supercritical fluid extraction (SFE), usually with carbon dioxide and, often, with a modifier, has become of increasing interest in the last few years because of its selectivity, preconcentration effect, efficiency, simplicity, rapidity, cleanness, and safety, mainly concerning the extraction of organic compounds prior to separation and detection by chromatographic techniques. It has several advantages over classical solvent extractions, in comparison with recent extraction techniques. Approaches to obtain quantitative extractions, including fluid choice, extraction flow rate, modifiers, pressure, and temperature, are presented, as well as the potential for SFE to extract polynuclear aromatic hydrocarbons (PAHs) from soils, sediments, and biota. Improvements and new environmental applications are also reported. 

This chapter reports the results of experimentation designed to examine the extraction and characterization of petroleum hydrocarbons, including PAHs, from marine sediments. The efficiencies of several methods for the extraction of PAHs from marine sediments were compared, and the ability of these extraction methods [followed by gas chromatographic-mass spectrometric (GC-MS) analysis] to reproduce consistently AHDs and PCDs from contaminated sediments was exam-... 

Traditionally, the extraction of PAHs from solid samples has been conducted using a Soxhlet method, which, while being efficient, usually takes more than 6 h and uses large volumes of solvent. Several reports have indicated that PAHs can be extracted from solid matrices such as soil and plant and animal tissues... 

The pressure in PLE is not a significant variable to optimize, because its role is simply to maintain the solvent in its liquid state. The main variables to optimize are extraction time and temperature, which considerably simplifies the experimental design. The main advantages of PLE are fastness (around 15 min), low amounts of toxic organic solvents are required (between 15 and 40 mL), and several samples can be extracted simultaneously (up to 24). However, the instrumentation is much more expensive than Soxhlet or even microwaves. EPA method 3545 uses PLE in the determination of semivolatile organic compounds from solid samples [139], which can be extended to solid devices used to trap PAHs in air monitoring. Furthermore, PLE has proven to be an efficient method to extract analytes from complex samples, with efficiencies comparable to Soxhlet extraction [140],... 

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