Solid phase extraction column chromatography

Liquid-liquid partitioning Solid-phase extraction Column chromatography... 

Besides solid-phase extraction, column chromatography is also often used for cleanup and purification of polyphenolics from plant material. Ionic adsorbants (polyvinylpyrrolidone or PVP, polyamides, and Sephadex LH-20) and Amberlite XAD-2 resin have been used to isolate and purify polyphenolics from crude extracts. For the separation of polyphenolics from plant material, column chromatography using Sephadex LH-20, a gel-filtration matrix, is often used with various eluting solvents (Park and Lee, 1996). The most widely used solvents for column chromatography are aqueous methanol and aqueous ethanol. 

Keywords Pressurized liquid extraction supercritical fluid extraction ultra-sound-assisted extraction microwave-assisted extraction matrix solid-phase extraction high-performance liquid chromatography gas chromatography liquid-liquid extraction solid phase extraction column chromatography... 

Cleanup A practical term used to describe the handling of a sample before the measuring step. For example, after the pesticides are extracted from a vegetable, the extract may contain fats and plant waxes that will interfere with the determination of the pesticides. These fats and waxes are removed by solid phase extraction, column chromatography, or gel permeation chromatography, and the extract then is said to be cleaned up,... 

Figure 2.12 Schematic representation of an on-line SPE-GC system consisting of three switching valves (VI-V3), two pumps (a solvent-delivery unit (SDU) pump and a syringe pump) and a GC system equipped with a solvent-vapour exit (SVE), an MS instrument detector, a retention gap, a retaining precolumn and an analytical column. Reprinted from Journal of Chromatography, AIIS, A. J. H. Eouter et al, Analysis of microcontaminants in aqueous samples hy fully automated on-line solid-phase extraction-gas chromatography-mass selective detection , pp. 67-83, copyright 1996, with permission from Elsevier Science.

Mallat, E. and Barcelo, D., Analysis and degradation study of glyphosate and of aminomethylphosphonic in natural waters by means of polymeric and ion-exchange solid-phase extraction columns followed by ion chromatography-post-column derivatization with fluorescence detection, /. Chromatogr A, 823, 129, 1998. 

Asperger A. et al., 2002. Trace determination of priority pesticide in water by means of high-speed online solid-phase extraction-liquid chromatography-tandem mass spectrometry using turbulent-flow chromatography columns for enrichment and a short monolithic column for fast liquid chromatographic separation. J Chromatogr A 960 109. 

Elimination of coextracted materials and concentration of tetracyclines have also been accomplished using mixed-phase extraction membranes with both re-versed-phase and cation-exchange properties (294,295), or solid-phase extraction columns packed with cation-exchange materials such as CM-Sephadex C-25 (301), aromatic sulfonic acid (310), and carboxylic acid (283, 300). For the same purpose, metal chelate affinity chromatography has also been employed. In this technique, the tetracyclines are specifically absorbed on the column sorbent by chelation with copper ions bound to small chelating Sepharose fast flow column (278-281, 294-296). 

Solid-phase extraction columns offer a rough cleanup of the crude extract, which might nevertheless not be sufficient for some detection systems such as mass spectrometry. Some authors have proposed a combination of solid-phase extraction and liquid chromatography columns for extract cleanup (440). Other methods appeal to liquid chromatography on Cig columns with automated fraction collection. Fractions containing the analyte of interest were evaporated to dryness, yielding a residue that in most cases was suitable for gas chromatographic detection after suitable derivatization (445, 437). 

To eliminate or reduce interference and concentrate the analyte(s), the primary sample extract can further be subjected to various types of cleanup procedures including liquid-liquid partitioning, solid-phase extraction, immunoaffmity chromatography, and column-switching techniques (Table 29.17). In some instances, more than one of these procedures may be used in combination to enhance the cleanup efficiency. 

J Slobodnik, AC Hogenboom, JJ Vreuls, JA Rontree, BLM van Baar, WM A Niessen, UAT Brinkman. Trace-level determination of pesticide residues using on-line solid-phase extraction-column liquid chromatography with atmospheric pressure ionization mass spectrometric and tandem mass spectrometric detection. J Chromatogr A 741 59-74, 1996. 

Figure 5.2 Schematic representation of the final column-switching system (a) forward-flush position (b) back-flush position (further details are given in the text). Reprinted from Journal of Chromatography, A 828, A. K. Sakhi et al. Quantitative determination of endogenous retinoids in mouse embryos by high-performance liquid chromatography with on-line solid-phase extraction, column switching and electrochemical detection , pp. 451-460, copyright 1998, with permission from Elsevier Science.

ON-LINE SOLID-PHASE EXTRACTION-LIQUID CHROMATOGRAPHY COLUMN-SWITCHING TECHNIQUE... 

Christie, W.W. 1989. Silver ion chromatography using solid-phase extraction columns packed with a bonded-sulfonic acid phase. /. Lipid Res. 30 1471-1473. 

A. Caballo-Lopez, M.D. Luque de Castro, Continuous ultrasound-assisted extraction coupled to on line filtration—solid-phase extraction—column liquid chromatography—post column derivatisation—fluorescence detection for the determination of N-methylcarbamates in soil and food, J. Chromatogr. A 998 (2003) 51. 

Furuno, K. Gomita, Y Araki, Y. Fukuda, T. Clonazepam serum Ifevels in epileptic patients determined simply and rapidly by high-performance liquid chromatography using a solid-phase extraction column. Acta Med.Okayama., 1991, 45, 123-127... 

Figure 3.9. Schematic diagram of an automated on-line solid-phase extraction-gas chromatography system. Large volume on-column injection with an early solvent vapor exit and retaining precolumn is used for sample transfer. (From ref. [117] Elsevier).

Figure 4 Elution patterns of hyoscine (scopolamine) and its dehydrated metabolite, apohyoscine, from Cis SPE columns. Hyoscine (A) or apohyoscine (B) eluted with 40% (v/v) methanoliwater and hyoscine (C) or apohyoscine (D) eluted with 50% (v/v) metha-noliwater. The latter eluent was chosen for the assay as >90% of hyoscine was recovered in the first milliliter, whereas <5% of the apohyoscine was eluted in this volume. Washing with 20% (v/v) methanol removed the majority of the urinary pigments but not the hyoscine. (Reproduced with permission from Whelpton R, Hurst PR, Metcalfe RF, and Saunders SA (1992) Liquid chromatographic determination of hyoscine (scopolamine) in urine using solid phase extraction Biomedical Chromatography 6. 198-204 John Wiley Sons Ltd.)...

Amide herbicides - preconcentration using SPMDs then bioassay. (2) Diethanol amides by solid-phase extraction-liquid chromatography-atmospheric pressure chemical ionization/electrospray ionization mass spectrometry (SPE-LC-APCI/ESI-MS) o-Phthaldialdehyde derivatization then reversed-phase LC with fluorescence defecfion. Chiral derivafizafion permifs separation of optical isomers on standard LC columns Anion exchange LC Ion-pair liquid chromatography... 

Solid-phase extraction is also often used to remove interfering coextracted compounds. Solid-phase extraction columns contain either non-polar reversed-phase Cig sorbents or polar sorbents (such as alumina, aminopropyl acid, and propylsulfonic acid). Matrix solid-phase dispersion cleanup using reversed-phase Cig material has been also employed for the determination of oxohnic acid in catfish muscle.In-tube solid-phase microextraction (SPME) based on poly(methacrylic acid-ethylene glycol dimethacrylate) (MAA-EGDMA) monolith coupled to high-preformance liquid chromatography (HPLC) with ultraviolet (UV) and fluorescence detection (FED) was... 

Silver-ion chromatography can be a useful technique for isolation of a fraction enriched in CLA, but it can also afford unrivaled analytical separations. Silver-ion thin-layer chromatography (TLC) is best regarded as an enrichment method. With a mobile phase such as hexane/diethyl ether (9 1, vol/vol), CLA as the methyl ester elutes with cis-monoenes, rather than with a diene fraction with toluene as mobile phase, it elutes just ahead of the cw-monoenes (10). Alternatively, solid-phase extraction columns with bonded sulfonic acid moieties converted to the silver-ion form can be used with a simple elution scheme to obtain a combined monoene-CLA fraction (2,11). 

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