Abstract
Solvent extraction remains one of the fundamental sample preparation techniques in the analysis of environmental solid samples, but organic solvents are toxic and environmentally harmful, therefore one of the possible greening directions is its miniaturization. The present review covers the relevant research from the field of application of microextraction to the sample preparation of environmental solid samples (soil, sediments, sewage sludge, dust etc.) published in the last decade. Several innovative liquid-phase microextraction (LPME) techniques that have emerged recently have also been applied as an aid in sample preparation of these samples: single-drop microextraction (SDME), hollow fiber-liquid phase microextraction (HF-LPME), dispersive liquid-liquid microextraction (DLLME). Besides the common organic solvents, surfactants and ionic liquids are also used. However, these techniques have to be combined with another technique to release the analytes from the solid sample into an aqueous solution. In the present review, the published methods were categorized into three groups: LPME in combination with a conventional solvent extraction; LPME in combination with an environmentally friendly extraction; LPME without previous extraction. The applicability of these approaches to the sample preparation for the determination of pollutants in solid environmental samples is discussed, with emphasis on their strengths, weak points and environmental impact.
Highlights
Solvent extraction (SE) remains one of the fundamental techniques employed prior to the analysis of the environmental contaminants in solid samples due to its high efficiency in transferring the compounds of interest from the frequently complex sample matrix into an analytical instrument-friendly solution
Organic solvents are recognized as problematic for several reasons: most of them are toxic to living organisms and harmful to the environment, special care has to taken for their proper disposal; they should be of high grade purity to avoid the contamination of extracts in trace analysis, and this alone significantly contributes to the high cost of analysis
Solvent extraction remains an important sample preparation technique in the environmental analysis of solid environmental samples because of its superior capacity to disrupt the sorption of pollutants to the solid particles and transfer them to the solution amenable to analysis
Summary
Solvent extraction (SE) remains one of the fundamental techniques employed prior to the analysis of the environmental contaminants in solid samples due to its high efficiency in transferring the compounds of interest from the frequently complex sample matrix into an analytical instrument-friendly solution. An example of a greener solvent introduced in the environmental sample preparation is supercritical water extraction (SWE) or pressurized hot water extraction (PHWE): water at temperatures up to 650 K and sufficiently high pressure becomes less polar, less viscous and more applicable to the extraction of organic contaminants of lower polarity, but the disadvantages of its use are rather low extraction yields, difficulties with subsequent solvent evaporation and incompatibility with thermally unstable compounds [2,3] Another example are ionic liquids (IL), which, synthetic compounds, are considered more environmentally friendly because of their low volatility and lower toxicity compared to conventional organic solvents [2,3,4]. The emphasis of the present review is on the research published in the last decade; some older literature will be considered whenever necessary to facilitate the understanding of subsequent advances
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