Liquid-liquid-liquid microextraction for sample preparation of biological fluids prior to capillary electrophoresis.
TL;DR: Liquid-liquid-liquid microextraction (LLLME) served as a technique for sample cleanup since large molecules, acidic compounds, and neutral components were not extracted into the acceptor phase.
Abstract: Methamphetamine as a model compound was extracted from 2.5-mL aqueous samples adjusted to pH 13 (donor solution) through a thin phase of 1-octanol inside the pores of a polypropylene hollow fiber and finally into a 25-microL acidic acceptor solution inside the hollow fiber. Following this liquid-liquid-liquid microextraction (LLLME), the acceptor solutions were analyzed by capillary zone electrophoresis (CE). Extractions were performed in simple disposable devices each consisting of a conventional 4-mL sample vial, two needles for introduction and collection of the acceptor solution, and a 8-cm piece of a porous polypropylene hollow fiber. From 5 to 20 different samples were extracted in parallel for 45 min, providing a high sample capacity. Methamphetamine was preconcentrated by a factor of 75 from aqueous standard solutions, human urine, and human plasma utilizing 10(-1) M HCl as the acceptor phase and 10(-1) M NaOH in the donor solution. In addition to preconcentration, LLLME also served as a technique for sample cleanup since large molecules, acidic compounds, and neutral components were not extracted into the acceptor phase. Utilizing diphenhydramine hydrochloride as internal standard, repetitive extractions varied less than 5.2% RSD (n = 6), while the calibration curve for methamphetamine was linear within the range 20 ng/microL to 10 micrograms/mL (r = 0.9983). The detection limit of methamphetamine utilizing LLLME/CE was 5 ng/mL (S/N = 3) in both human urine and plasma.
Citations
More filters
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: 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: Electrokinetic migration across thin artificial liquid membranes may be an interesting tool for future isolation within chemical analysis and may serve as an efficient tool for controlling the transport selectivity.
582 citations
TL;DR: The liquid-phase microextraction (LPME) as mentioned in this paper is a sample-preparation technique that uses a hollow fiber impregnated with an organic solvent to accommodate or protect microvolumes of acceptor solution.
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 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).
565 citations
TL;DR: The comprehensive study summarizes the latest progress on assorted classes of ILs along with discussing their prospective applications in the first half and the synthesis of homo/heterogeneous ILs is thoroughly elaborated in the second half.
522 citations
References
More filters
TL;DR: Sample stacking is a sample on-column concentration technique in high performance capillary electrophoresis (HPCE) as mentioned in this paper, but the amount of sample which can be loaded into the column in conventional sample stacking is rather limited because of disturbance caused by the low-concentration sample buffer.
Abstract: Sample stacking is a sample on-column concentration technique in high-performance capillary electrophoresis (HPCE). However, the amount of sample which can be loaded into the column in conventional sample stacking is rather limited because of disturbance caused by the low-concentration sample buffer. This report describes a technique of stacking an extremely large sample volume into narrow bands. The technique is based on the principal that the local electrophoretic velocity of the ions inside the sample buffer is much faster than the bulk electroosmotic velocity of the solution
490 citations
TL;DR: In this paper, a theoretical description of the sample self-stacking effect in zone electrophoresis is given, which applies to samples that contain a high concentration of an ionic component with high mobility and like charge.
208 citations
TL;DR: In this article, the column-coupling configuration of the separation unit was studied and the inherent concentrating power of the ITP stage was effective in achieving a high volume reduction of the injected sample so that the ZE separations with 2-3 μm plate heights could be achieved in 300 μm I.D.
181 citations
TL;DR: In this article, a solvent microextraction technique was developed to perform simultaneous forward and back-extraction across a microliter-size organic liquid membrane, where the solvent phase (o) consisting of 40 or 80 μL of n-octane, is layered over 0.5 or 1.0 mL of aqueous sample phase (a1) contained in a 1- or 2-mL microreaction vial and is stabilized against mechanical disruption by a small Teflon ring, even when the a1 phase is stirred at a speed of 2000 rpm.
Abstract: A solvent microextraction technique has been developed to perform simultaneous forward- and back-extraction across a microliter-size organic liquid membrane. The organic liquid membrane phase (o), consisting of 40 or 80 μL of n-octane, is layered over 0.5 or 1.0 mL of aqueous sample phase (a1) contained in a 1- or 2-mL microreaction vial and is stabilized against mechanical disruption by a small Teflon ring, even when the a1 phase is stirred at a speed of 2000 rpm. A 0.1- or 0.2-mL aqueous receiving phase (a2) is layered over the o phase. After extraction for a prescribed time, an aliquot of the a2 phase is injected directly into an HPLC for quantification. The technique is efficient and selective for ionizable compounds. In 30 min, the model compounds, mephentermine and 2-phenylethylamine, in the a1 phase buffered at pH 13 are 100% and 90% extracted, respectively, into the a2 phase buffered at pH 2.1. A kinetic model has been developed, based on the Whitman two-film theory, to describe the extraction pro...
160 citations
TL;DR: Two methods were developed using capillary electrophoresis to concentrate urinary constituents in order to collect adequate amounts of separated analytes, using an analyte concentrator containing an antibody covalently bound to a solid support material.
Abstract: Two methods were developed using capillary electrophoresis to concentrate urinary constituents in order to collect adequate amounts of separated analytes. the first method utilizes multiple capillaries arranged in bundles and coupled to a single capillary through a glass connector. the second method consists of the use of an analyte concentrator containing an antibody covalently bound to a solid support material. Both methods allow loading of increased amounts of samples into the capillary, and the continuous collection of purified material in nanogram-microgram quantities. the samples collected by the two methods were further analyzed by mass spectrometry.
158 citations