Atmospheric microwave-assisted extractions

Example 7.4 Atmospheric Microwave-Assisted Extraction of Polycyclic Aromatic Hydrocarbons from Contaminated Soil... 

Figure 7.13 Results obtained for the atmospheric microwave-assisted extraction of various polycyclic aromatic hydrocarbons from contaminated soil, and comparison with those obtained from Soxhlet extraction , Soxhlet , aMAE 1, naphthalene 2, acenaphthylene 3, acenaphthene 4, fluorene 5, phenanthene 6, anthracene 7, fluoranthene 8, pyrene 9, benz[a]anthracene 10, chrysene 11, benzo[fr, ]fluoranthene 12, benzo[a]pyrene 13, indeno[l,2,3-cd]pyrene 14, benzo[gfe ]pyrene [1] (cf. DQ 7.10).

As already observed for atmospheric microwave-assisted extraction (see Figure 7.13 above), it is found that the recoveries of polycyclic aromatic hydrocarbons from soil are similar irrespective of the extraction method used. In addition, similar precision is achieved in both cases. 

First of all, it is important to identify what the acronyms represent. The following have been used aMAE, atmospheric microwave-assisted extraction SFE, supercritical fluid extraction pMAE, pressurized microwave-assisted extraction PFE, pressurized fluid extraction ASE, accelerated solvent extraction MSPD, matrix solid-phase dispersion. 

Saim, N., Dean, J. R., Abdullah, M. P., and Zakaria, Z., Extraction of polycyclic aromatic hydrocarbons from contaminated soil using Soxhlet extraction, pressurized and atmosphereic microwave-assisted extraction, supercritical fluid extraction and accelerated solvent extraction,... 

In extraction, analyte is dissolved in a solvent that does not necessarily dissolve the entire sample and does not decompose the analyte. In a typical microwave-assisted extraction of pesticides from soil, a mixture of soil plus acetone and hexane is placed in a Teflon-lined bomb (Figures 28-8 and 28-13) and heated by microwaves to 150°C. This temperature is 50° to 100° higher than the boiling points of solvents at atmospheric pressure. Pesticides dissolve, but the soil remains behind. The liquid is then analyzed by chromatography. 

Most studies about the microwave-assisted extraction of PAHs from solid samples have been conducted using closed-vessel systems [12,214,226,236,239-246] and only a few with open-vessel focused microwave devices [57,247-252]. Because open-vessel systems operate at atmospheric pressure, the extraction vessel can be used as a reactor in order to perform on-line purification pretreatments of the total extracts (reagents can be readily added to the medium) [53] or directly introduce the extract into the determination instrument, as in the focused microwave-assisted extractor with on-line fluorescent monitoring of Fig. 5.10, which provides a matrix-independent approach to the extraction of PAHs [61]. 

A study was carried out for LEE by the Soxhlet method and microwave-assisted extraction for the determination of the priority phenols in soil samples. Recoveries varied from 67 to 97% with RSD between 8 and 14% for LEE, and >70% for the MAP, except for nitrophenols that underwent degradation when the latter method was applied. LOD was from 20 ngg for 2,4-dimethylphenol to 100 ngg for pentachlorophenol. The best detection method for EC was atmospheric pressnre chemical ionization MS (APCI-MS). The most abnndant ions obtained by this detection method were [M — H] for the lowly chlorinated phenols and [M — H — HCl] for tri-, tetra- and pentachlorophenols . 

Pineiro-Iglesias, M., Lopez-Mahia, P., Vazquez-Bianco, E., Muniategui-Lorenzo, S., Prada-Rodriguez, D., and Fernandez-Fernandez, E., Microwave assisted extraction of polycyclic aromatic hydrocarbons from atmospheric particulate samples, Fresenius J Anal. Chem., 367, 29-34, 2000. 

Wurl O, Potter JR, Obbard JP, Durville C (2006) Persistent organic pollutants in the equatorial atmosphere over the open Indian Ocean. Environ Sci Technol 40 1454-1461 Yang JS, Lee DW, Lim H (2003) Microwave-assisted extraction (MAE) of polychlorinated biphenyls and polychlorinated dibenzo-p-dioxins from fly ash and sea sediments effect of water and removal of interferences. J Liq Chromatogr Rel Technol 26 803-818... 

Castro,D., Slezakova, K.,Ohva-Teles,M.T.,Delerue-Matos, C., Alvim-Ferraz, M.C., Morais, S. Pereira M.C. 2009. Analysis of polycychc aromatic hydrocarbons in atmospheric particulate samples by microwave-assisted extraction and hquid chromatography. Journal of Separation Science 32 501—510. 

Sensitive, rapid, simple, and accurate analytical methods have been developed to determine PAHs and their derivatives in the atmospheric particles. Extensively used are GC and coupled methods like GC-FTD, GC-MS, and HPLC-EL as highly efficient separation tools have been used for analyzing aU kinds of samples. The direct determination of traces of PAHs and their derivatives by modem chromatographic techniques is still difficult. There are some limitations associated with the insufficient sensitivity of these techniques and also problems related to matrix interference. For instance in the case of samples of atmospheric particulates, extraction methods of PAHs and their derivatives include traditional Soxhlet extraction, ultrasonic extraction, supercritical fluid extraction, microwave-assisted extraction, and accelerated solvent extraction. ... 

Mermet, J.M. Focused-microwave-assisted reactions atmospheric-pressure acid digestion, on-line pretreatment and acid digestion, volatile species production, and extraction. In Kingston, H.M., Haswell, S.J. (eds.) Microwave-Enhanced Chemistry. Fundamentals, Sample Preparation, and Applications. ACS, Washington, DC (1997)... 

Dynamic systems for high-pressure microwave treatment were developed much later than open-vessel systems. Operating under a high pressure reduces the flexibility afforded by working at atmospheric pressure. However, some recently developed devices allow microwave-assisted high-pressure digestion and extraction in a dynamic manner [33,34]. 

J. R. J. Pare, G. Matni, V. Yaylayan, J. M. R. Belanger, K. Li, C. Rule, B. Thibert, D. Mathe, and P. Jacquault, Novel Approaches in the Use of the Microwave-Assisted Process (MAP Part I Extraction of Fat from Meat and Meat Products Under Atmospheric Pressure Conditions , submitted for publication. 

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