Microwave assisted extraction of organic compounds

Abstract

Abstract. Microwave energy has been developed recently for the extraction of organic compounds from environmental matrices after its use in inorganic chemistry for trace metal analysis. The development in microwave techniques has occurred because of a need for a rapid, safe and cheap method. Conventional techniques for the extraction of solid matrices (such as Soxhlet) are time and solvent consuming and the analysis of numerous samples in environmental studies is limited by the extraction step. This review recalls the importance of the extraction step in the analytical procedure for the analysis of organic contaminants and the principles of extraction of solid matrices (sediment, soil, air particulate matter...). The theory of microwave heating is summarised and the microwave ovens used in analytical chemistry are described. Then, the review attempts to summarise all the studies about microwave assisted extraction for organic contaminants, on one hand in multimode microwave ovens in closed vessels and on the other hand in focused microwave ovens at atmospheric pressure. The microwave assisted extraction methods of volatile compounds are summarised. Finally, advantages of methods compared to conventional extraction are discussed.Key words. Microwave -extraction -organic contaminants. Analusis, 1999, 27, 259-271 © EDP Sciences, Wiley-VCH 1999 * Correspondence and reprints. Received October 20, 1998 revised December 09, 1999; accepted January 19, 1999. Article available at http://analusis.edpsciences.org or http://dx.doi.org/10.1051/analusis:1999116 soils, air particulate matter...). The theory of microwave heating is summarised and the microwave ovens used in analytical chemistry are described. Then, the review attempts to summarise all the studies about microwave assisted extraction of non and semi-volatile organic contaminants, on one hand in multimode microwave oven in closed vessels and on the other hand in focused microwave ovens at atmospheric pressure. The influence of parameters such as time, temperature, power, nature of solvent, nature of matrix, moisture content and the stability of compounds are discussed. The microwave assisted extraction methods of volatile compounds are summarised. Finally, advantages of these methods compared to conventional extraction are reviewed. Importance of the extraction step in the analytical procedureNatural samples can rarely be used in their raw state. Their nature must be compatible with the detection method. The analysis of organic contaminants requires pre-treatment of the sample. Different steps of sampling, extraction and purification are necessary before the determination and the quantification of individual compounds.The principal step of the sample treatment is the extraction of analytes from matrix, which consists of transfer of the compounds into a solvent. Extraction is rarely selective. The raw extract is then constituted of studied compounds at trace level but also of co-extracted compounds (endogenous compounds, macromolecules, other contaminants...)...

Techniques for extraction of bioactive compounds from plant materials: A review

“…They are made up of two oscillating fields that are perpendicular such as electric field and magnetic field. The principle of heating using microwave is based upon its direct impacts on polar materials (Letellier and Budzinski, 1999). Electromagnetic energy is converted to heat following ionic conduction and dipole rotation mechanisms (Jain, 2009).…”

Development of a one-step microwave-assisted extraction procedure for highly efficient extraction of multiclass fungicides in soils

“…2,10 However, these methods usually generate too much solvent waste and are also labor intensive and time consuming. 10 Recently, a number of alternative methods such as solid phase microextraction (SPME), 11,12 supercritical uid extraction (SFE), [13][14][15] pressurized liquid extraction (PLE), [16][17][18] ultrasonic solvent extraction (USE), 2,4,10 and microwave assisted extraction (MAE) 7,8,[19][20][21][22][23][24][25][26] have been commonly used for the extraction of pesticides in soil. MAE was introduced in 1986 by Ganzler et al 27 and has been successfully applied to extract organic compounds from various solid and liquid matrices.…”

“…33 For the closed vessel extraction systems, the major parameters affecting the pesticide extraction efficiency by MAE are temperature, irradiation time, irradiation power, and the nature and volume of the solvent. 22,26,34 Experiments were performed using ve replicates (n ¼ 5) and the extraction efficiencies were evaluated from the recoveries (R, %). 32,35 However, the optimization results obtained couldn't be compared since there are no literature reports available for the analysis of the same kinds of fungicide in soil using MAE.…”

“…In most of the cases, matrix moisture improved the extraction recovery. 22 A 10% moisture level in the matrix showed recoveries of >57% for all fungicides studied, and was therefore selected for optimal MAE efficiency.…”

Study of the possible migration risks of food contact materials for children under 3 years

“…The processes involved in heat transfer during microwave heating are different from those during conduction or convection heating, and consequently unpredictable migration behaviour could be expected (Letellier & Budzinski 1999;Alin & Hakkarainen 2012).…”