Solvent microextraction into a single drop.
TL;DR: An analytical technique is described which combines solvent extraction with gas chromatographic (GC) analysis in a simple and inexpensive apparatus involving very little solvent consumption and is in good agreement with a convective-diffusive kinetic model.
Abstract: An analytical technique is described which combines solvent extraction with gas chromatographic (GC) analysis in a simple and inexpensive apparatus involving very little solvent consumption. A small drop (8 μL) of a water-immiscible organic solvent, containing an internal standard, is located at the end of a Teflon rod which is immersed in a stirred aqueous sample solution. After the solution has been stirred for a prescribed period of time, the probe is withdrawn from the aqueous solution, and the organic phase is sampled with a microsyringe and injected into the GC for quantification. The observed rate of solvent extraction is in good agreement with a convective−diffusive kinetic model. Analytically, the relative standard deviation of the method is 1.7% for a 5.00-min extraction of the analyte 4-methylacetophenone into n-octane.
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TL;DR: The ability of DLLME technique in the extraction of other organic compounds such as organochlorine pesticides, organophosphorus pesticides and substituted benzene compounds were studied.
2,959 citations
TL;DR: This review focuses on the extra steps in sample preparation for application of DLLME in different matrixes such as food, biological fluids and solid samples and its applications in conjunction with different extraction techniques such as solid-phase extraction, solidification of floating organic drop and supercritical fluid extraction are summarized.
851 citations
TL;DR: Under the optimum conditions, the enrichment factors and extraction recoveries were high and ranged between 789-1070 and 78.9-107%, respectively, while the linear range was wide and limit of detections were very low and were between 3 to 20 pg/mL for most of the analytes.
826 citations
TL;DR: In this paper, the authors discuss liquid-phase microextraction with the focus on extraction principles, historical development and performance, and discuss the current trend towards simplification and miniaturization of sample preparation and decreasing the quantities of organic solvents used.
Abstract: The development of faster, simpler, inexpensive and more environmentally-friendly sample-preparation techniques is an important issue in chemical analysis. Recent research trends involve miniaturization of the traditional liquid-liquid-extraction principle by greatly reducing the acceptor-to-donor ratio. The current trend is towards simplification and miniaturization of sample preparation and decreasing the quantities of organic solvents used. We discuss liquid-phase microextraction with the focus on extraction principles, historical development and performance.
698 citations
TL;DR: In this article, the authors measured the amount of a sample compound extracted into a 1-μL drop of n-octane suspended in a stirred aqueous solution from the tip of a microsyringe needle.
Abstract: The amount of a sample compound extracted into a 1-μL drop of n-octane suspended in a stirred aqueous solution from the tip of a microsyringe needle is measured by gas chromatography (GC) as a function of time. The observed extraction rate curve is first order and yields the overall mass transfer coefficient for the sample compound, βo. For a given compound, βo varies linearly with stirring rate. Among the four compounds malathion, 4-methylacetophenone, 4-nitrotoluene, and progesterone, at a given stirring rate, βo is linearly proportional to the diffusion coefficient of the compound (Daq). This supports the film theory of convective−diffusive mass transfer, as opposed to the penetration theory. The relative standard deviation of the GC signal for 4-methylacetophenone after a 1.00 min extraction at 1500 rpm is 1.5%, which suggests that the system exhibits excellent potential as a tool for rapid analysis by solvent extraction/GC.
531 citations
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25 May 1984TL;DR: An overview of diffusion and separation processes brings unsurpassed, engaging clarity to this complex topic as mentioned in this paper, which is a key part of the undergraduate chemical engineering curriculum and at the core of understanding chemical purification and reaction engineering.
Abstract: This overview of diffusion and separation processes brings unsurpassed, engaging clarity to this complex topic. Diffusion is a key part of the undergraduate chemical engineering curriculum and at the core of understanding chemical purification and reaction engineering. This spontaneous mixing process is also central to our daily lives, with importance in phenomena as diverse as the dispersal of pollutants to digestion in the small intestine. For students, Diffusion goes from the basics of mass transfer and diffusion itself, with strong support through worked examples and a range of student questions. It also takes the reader right through to the cutting edge of our understanding, and the new examples in this third edition will appeal to professional scientists and engineers. Retaining the trademark enthusiastic style, the broad coverage now extends to biology and medicine.
5,195 citations
TL;DR: The solid phase microextraction (SPME) technique as mentioned in this paper involves exposing a fused silica fiber that has been coated with a stationary phase to and aqueous solution containing organic contaminants.
Abstract: The solid-phase microextraction (SPME) technique involves exposing a fused silica fiber that has been coated with a stationary phase to and aqueous solution containing organic contaminants. The analytes partition into the stationary phase until an equilibrium has been reached, after which the fiber is removed from the solution and the analytes are thermally desorbed in the injector of a gas chromatograph
598 citations
TL;DR: In this paper, the Peclet number is used as the similarity criterion for longitudinal mixing of fluids in flow, which is analogous to and has the same units as the coefficient of molecular diffusion.
532 citations
TL;DR: In this paper, a novel material for separations has been developed in which efficient chromatographic particles are enmeshed in a network of PTFE fibrils to form a strong, porous sheet or "membrane".
249 citations
01 Nov 1980
TL;DR: In this article, a review of solvent extraction of metal species by organic solution of acidic, basic, and neutral reagents has been conducted by considering the contribution of both chemical reactions and transport processes on the rate of extraction.
Abstract: The kinetics of solvent extraction of metal species by organic solution of acidic, basic, and neutral reagents has been reviewed by considering the contribution of both chemical reactions and transport processes on the rate of extraction. The relative predominance of slow chemical reactions and diffusion processes has been shown to depend, in a critical way, both on the hydrodynamic conditions present in the extracting apparatus and on the specific nature and composition of the chemical system involved in the extraction. The general criteria that can help to distinguish between extraction kinetics controlled either by mass transport or chemical reactions have been reviewed. These criteria involve the experimental determination of the influence of a rather large number of physical and chemical variables on the rate of extraction and do not always lead to unambiguous conclusions. The reviewed literature has allowed to draw the following conclusions: (1) because of a lack of complete characterization (especially in terms of hydrodynamics, interfacial pressure, and sufficiently wide concentration ranges), much of the early work on solvent extraction kinetics has rarely led to the definite identification of the rate determining processes; as a consequence, correct extrapolation to the different experimental conditions that are met in practicalmore » analytical or technological separations has been often impossible; and (2) more recently a certain number of extraction kinetics studies have appeared which have been carried out in hydrodynamically controlled conditions, exploring a large range of compositions of the species and with knowledge of the interfacial properties of the biphasic system; such studies have contributed to the emergence of a general pattern for the solvent extraction kinetics which is summarized.« less
169 citations