Matrix solid-phase extraction

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... 

Matrix solid-phase extraction (MSPE) is a recently introduced alternative to SPE in which samples are thoroughly mixed with a solid substrate, then packed into a column and washed and eluted with solvents, so the sample cleanup and analytes extraction are carried out in a single step. The solid support can be CIS- or C8-bonded silica ° 2 or Amberlite XAD-2, and even the use of sea sand as solid substrate has also been reported recently. As in the traditional chromatographic and SPE procedures, extraction conditions, especially the composition of the eluents, need to be optimized before the extraction. 

For drug products, sample preparation may involve grinding, extraction, and filtration (31-35). For samples with a more complicated matrix, solid phase extraction (SPE) and other sample preparation techniques can be used to remove interfering species and to increase sensitivity (36-41). The procedure needs to ensure sufficient recovery of target analytes for accuracy and sensitivity. 

Solid-Phase Extractions In a solid-phase extraction the sample is passed through a cartridge containing solid particulates that serve as the adsorbent material. For liquid samples the solid adsorbent is isolated in either a disk cartridge or a column (Figure 7.17). The choice of adsorbent is determined by the properties of the species being retained and the matrix in which it is found. Representative solid adsorbents... 

Two examples from the analysis of water samples illustrate how a separation and preconcentration can be accomplished simultaneously. In the gas chromatographic analysis for organophosphorous pesticides in environmental waters, the analytes in a 1000-mL sample may be separated from their aqueous matrix by a solid-phase extraction using 15 mb of ethyl acetate. After the extraction, the analytes are present in the ethyl acetate at a concentration that is 67 times greater than that in... 

In a solid-phase extraction the analytes are first extracted from their solution matrix into a solid adsorbent. After washing to remove impurities, the analytes are removed from the adsorbent with a suitable solvent. Alternatively, the extraction can be carried out using a Soxhlet extractor. 

Two approaches have been used to separate the analyte from its matrix in particulate gravimetry. The most common approach is filtration, in which solid particulates are separated from their gas, liquid, or solid matrix. A second approach uses a liquid-phase or solid-phase extraction. 

Extraction Eiltering limits particulate gravimetry to solid particulate analytes that are easily separated from their matrix. Particulate gravimetry can be extended to the analysis of gas-phase analytes, solutes, and poorly filterable solids if the analyte can be extracted from its matrix with a suitable solvent. After extraction, the solvent can be evaporated and the mass of the extracted analyte determined. Alternatively, the analyte can be determined indirectly by measuring the change in a sample s mass after extracting the analyte. Solid-phase extractions, such as those described in Ghapter 7, also may be used. 

Volatile analytes can be separated from a nonvolatile matrix using any of the extraction techniques described in Ghapter 7. Fiquid-liquid extractions, in which analytes are extracted from an aqueous matrix into methylene chloride or other organic solvent, are commonly used. Solid-phase extractions also are used to remove unwanted matrix constituents. 

Description of Method. Fluoxetine, whose structure is shown in Figure 12.31a, is another name for the antidepressant drug Prozac. The determination of fluoxetine and its metabolite norfluoxetine. Figure 12.31 b, in serum is an important part of monitoring its therapeutic use. The analysis is complicated by the complex matrix of serum samples. A solid-phase extraction followed by an HPLC analysis using a fluorescence detector provides the necessary selectivity and detection limits. 

This sample preparation involved, firstly, an extraction and the elimination of the solid matrix by filtration and, secondly, a concentration procedure employing a solid phase extraction cartridge. The compounds of interest were separated solely by dispersive interactions with the reversed phase. In the example given, the corn meal was spiked with the aflatoxins. 

A technique that attempts to combine the extraction and SPE into a single step is matrix solid-phase dispersion (MSPD). In this technique, a nonpolar (such as Cig) SPE sorbent is blended directly into tissue matrix, the mixture is packaged into an SPE cartridge, and the cartridge is eluted like a typical SPE cartridge. The advantage of MSPD is reduced sample size and increased efficiency due to a reduced number of steps. 

Beef kidney samples were analyzed for atrazine by dispersing 0.5-g portions of kidney with 2-g portions of XAD-7 HP resin for matrix solid-phase dispersion. " By using a mortar and pestle, a powder-like mixture was prepared that was subjected to subcritical extraction using ethanol-modified water at 100 °C and 50 atm. The ethanol-water extract was sampled using a CW-DVB SPME fiber for direct analysis using ion-trap GC/MS, and the recoveries were quantitative for atrazine at the 0.2 mg kg fortification level. 

Solid-phase sorbents are also used in a technique known as matrix solid-phase dispersion (MSPD). MSPD is a patented process first reported in 1989 for conducting the simultaneous disruption and extraction of solid and semi-solid samples. The technique is rapid and requires low volumes (ca. 10 mL) of solvents. One problem that has hindered further progress in pesticide residues analysis is the high ratio of sorbent to sample, typically 0.5-2 g of sorbent per 0.5 g of sample. This limits the sample size and creates problems with representative sub-sampling. It permits complete fractionation of the sample matrix components and also the ability to elute selectively a single compound or class of compounds from the same sample. Excellent reviews of the practical and theoretical aspects of MSPD " and applications in food analysis were presented by Barker.Torres et reported the use of MSPD for the... 

The extent of the cleanup depends on the sample matrix to be analyzed, the extraction procedure, the method of detection and the desired sensitivity. Generally, the cleanup method is liquid-liquid partitioning (LLP), but recently it has become simpler and more reliable to use solid-phase extraction (SPE) columns. 

A cleanup procedure is usually carried out to remove co-extracted matrix components that may interfere in the chromatographic analysis or be detrimental to the analytical instrument. The cleanup procedure is dependent on the nature of the analyte, the type of sample to be analyzed, and the selectivity and sensitivity of the analytical instrument used in the analysis. Preliminary purification of the sample extracts prior to chromatographic separation involves liquid-liquid partitioning and/or solid-phase extraction (SPE) using charcoal/Celite, Elorisil, carbon black, silica, or aminopropyl-silica based adsorbents or gel permeation chromatography (GPC). 

Diffusive sampler Membrane extraction (MESI) Liquid-liquid extraction (LLE) Solid-phase extraction (SPE) SPE-PTV-GC Solid-phase microextraction (SPME) Headspace GC (SHS, DHS) Large-volume injection (LVI) Coupled HPLC-GC Membrane extraction (MESI) Difficult matrix introduction (DMI) Conventional solvent extraction methods 1 Pressurised solvent extraction methods Headspace GC (SHS, DHS) Thermal desorption (TD, DTD) Pyrolysis (Py) Photolysis Photon extraction (LD) Difficult matrix introduction (DMI)... 

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