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Determination of organic compounds in water using dispersive liquid-liquid microextraction

Evolution of dispersive liquid-liquid microextraction method.

Dispersive liquid-liquid microextraction combined with gas chromatography-flame photometric detection. Very simple, rapid and sensitive method for the determination of organophosphorus pesticides in water

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.

https://profdoc.um.ac.ir/articles/a/1013566.pdf

Liquid-phase microextraction

The development of faster, simpler, inexpensive and more environmentally friendly sample-preparation techniques is an important issue in chemical analysis. Recent research trends involve miniaturisation of the traditional liquid-liquid extraction (LLE) principle by greatly reducing the acceptor-to-donor phase ratio. One of the emerging techniques in this area is liquid-phase microextraction (LPME), where a hollow fibre impregnated with an organic solvent is used to accommodate or protect microvolumes of acceptor solution. This novel methodology proved to be an extremely simple, low-cost and virtually solvent-free sample-preparation technique, which provided a high degree of selectivity and enrichment by additionally eliminating the possibility of carry-over between runs. This article presents the different modes and hollow-fibre configurations of LPME, followed by an up-to-date summary of its applications. The most important parameters and practical considerations for method optimisation are also discussed. The article concludes with a comparison of this novel method with solid-phase microextraction (SPME) and single-drop microextraction (SDME).

Developments in liquid-phase microextraction

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.

Solvent microextraction into a single drop.

A hanging microliter drop of 1-octanol is shown to be an excellent preconcentration medium for headspace analysis of volatile compounds in an aqueous matrix by gas chromatography (GC) or gas chromatography/mass spectrometry (GC/MS). Model compounds benzene, toluene, ethylbenzene, and o-xylene (BTEX) are conveniently and rapidly preconcentrated in the microdrop. An internal standard, decane, is present in the organic extracting solvent, and linear calibration curves of relative peak area versus aqueous concentration are obtained for the four model compounds. Detailed kinetic studies reveal that the overall rate of mass transfer is limited by both the aqueous-phase stirring rate and the degree of convection within the organic phase. The very low vapor pressure of 1-octanol results in minimal evaporation of the microdrop during the extraction time. This system represents an inexpensive, convenient, and precise sample cleanup and preconcentration method for the determination of volatile organic compounds at t...

Headspace solvent microextraction.

Single drop microextraction--development, applications and future trends.

A 1-μL drop of n-octane suspended from the tip of a microsyringe needle in 500 mL of stirred aqueous solution is used to extract unbound progesterone in the presence of 1% (w/v) bovine serum albumin (BSA) for analysis by gas chromatography (GC). The observed extraction kinetics are in good agreement with a proposed convective−diffusive mass transfer model which accounts for diffusion of both free and bound species in the aqueous Nernst diffusion film adjacent to the interface. The equilibrium binding constant, which can be measured both at equilibrium and at nonequilibrium extraction times, is in good agreement with literature values. The very small phase ratio employed (i.e., 2 × 10-6 mL of organic/mL of water) avoids perturbation of the aqueous solution equilibria.

Solvent microextraction as a speciation tool : Determination of free progesterone in a protein solution

This book offers both a practical as well a theoretical approach to Solvent Microextraction (SME) and will help analytical chemists to evaluate SME for a given sample preparation. Introductory chapters overview a comparison of SME with other sample preparation methods, a summary of the technical aspects, and a detailed theoretical treatment of SME. The book then describes the practical aspects of the technique, with detailed “how to” chapters devoted to the preparation and analysis of atmospheric, solid and liquid environmental, clinical and industrial samples. This text will serve as both a handy laboratory desk-reference and an indispensible instructional tool.

Michael A. Jeannot

Papers

Solvent microextraction into a single drop.

Headspace solvent microextraction.

Single drop microextraction--development, applications and future trends.

Solvent microextraction as a speciation tool : Determination of free progesterone in a protein solution

Solvent Microextraction: Theory and Practice