Solid phase sorbents

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... 

Beef muscle Homogenize, dilute with distilled water, centrifuge and filter to remove water-insoluble particulates extract onto solid-phase sorbents ITMS 50-100 ppb 20-50% Buchanan et al. 1995... 

Solid Phase Sorbents. Solid Phase Extraction Formats. Automated Solid Phase Extraction. Solid Phase Microextraction. Applications of SPE and SPME. 

Wachs, T. and Henion, J. 2003. A device for automated direct sampling and quantitation from solid-phase sorbent extraction cards by electrospray tandem mass spectrometry. Anal. Chem. 75 1769. 

T. Parkas, L Loo, J. Teuscher, and K. Kallury, "Rapid and Reproducible Extraction of Acrylamide in French Fries Using a Single Solid-Phase Sorbent," Am. Lab. New Ed. October 2003, p. 10.]... 

Finally, it is possible that the analyte and the sorbent may be chemically reactive toward each other such that the analyte becomes covalently bonded to the solid-phase sorbent. This type of sorption is generally detrimental to analytical recovery and may lead to slow or reduced recovery, also termed biphasic desorption. All of these interactions have the potential of operating simultaneously during sorption [8,54,55],... 

Finally, the presence of the solid-phase sorbent material improves the equilibrium of Reactions (7) and (8). By removing carbon dioxide from the products of the steam reforming process, equilibrium is shifted toward greater hydrogen production, reduced carbon monoxide and carbon dioxide concentrations, and increased fuel conversion. 

All individual methodologies described in the following, such as ion exchange, hydrophobic interaction, and affinity chromatography, are potentially usable in packed-bed mode as well as in fluid-bed mode if the solid phase sorbent meets the specific requirements of density and particle size. The only exception today is gel filtration, which requires a large number of plates for an acceptable resolution that the fluid bed cannot guarantee. 

Hydrophobicity is a very relative parameter that induces problems not only at the level of the determination of optimized operational conditions, but also at the level of the consistency of solid phase sorbents. 

As underlined in the introduction, all described methodologies for the purification of antibodies address preparative purposes at bench and industrial scales. They are diverse in the principle of adsorption-desorption, in their productivity aspect, in the purity of antibody that they are able to yield and, finally, in the exploitation cost. The latter depends not only on the initial cost of a solid phase sorbent, but also on run-to-run stability and consistency to withstand dozen or hundred or even thousand of cycles. 

In addition to the functionalities attached to the benzene ring in polystyrene, it is also possible to include in the polystyrene backbone different monomer units and generate solid phase sorbents with modified properties. It is common, for example, that the ion exchangers or solid phase sorbents contain a certain proportion of divinylbenzene DVB) used for crosslinking the polystyrene macromolecules. Contents around 8-12% DVB in styrene are common in commercial products. Other cross-linking substances can be used besides divinylbenzene, such as ethylenedimethacrylate. 

Chemical partitioning also occurs between water and solid phases and between air and solid phases, in a process most generally termed sorption. Types of sorption include adsorption, in which a chemical sticks to the two-dimensional surface of a solid, and absorption, in which a chemical diffuses into a three-dimensional solid. Chemical sorption in the environment is much more difficult to predict than is chemical partitioning between air and water, partly because the types of sorptive solid phases (sorbents) vary enormously, and partly because there are many different mechanisms by which sorption can occur. In this section, only partitioning between water and solid phases is considered. 

Figure 13 Solid-phase extraction recovery of two acidic compounds from four different solid-phase sorbents using a wash solvent of 5% acetonitrile and an elution solvent of 100% acetonitrile. The solid lines indicate the coefficient of variation associated with each determination. (From Ref. 31.)...

Wachs, T. Henion, J.A. Device for Automated Direct Sampling and Quantitation from Solid-Phase Sorbent Extraction Cards by Electrospray Tandem Mass Spectrometry, Anal. Chem. 75, 1769-1775 (2003). 

Solid-phase extraction (SPE) is a procedure in which an analyte, contained in a liquid phase, comes in contact with a solid phase (sorbent particles in a column or disk) and is selectively attracted to the surface of that solid phase. All other materials not adsorbed by chemical attraction or affinity remain in the liquid phase and go to waste. A wash solution is then usually passed through the sorbent bed to remove any loosely adsorbed contaminants from the sample matrix, yet retain the analyte of interest on the solid phase. Einally, an eluting solvent (usually an organic solvent such as methanol or acetonitrile that may be modified with acid or base) is added to the sorbent bed. This solvent disrupts the attraction between the analyte and solid phase that cause desorption,... 

Figure 1.1 illustrates the four-step process of SPE. First the solid-phase sorbent is conditioned (step 1). This simply means that a solvent is passed through the sorbent to wet the packing material and to solvate the functional groxips of the sorbent. Furthermore, the air present in the column is removed and the void spaces are filled with solvent. Typically the conditioning solvent is methanol, which is then followed with water or an aqueous buffer. The... 

If one considers that the contents of an SPE cartridge could be opened and placed in a beaker with analytes present and shaken, then sorption would occur between the analytes in solution and the solid-phase sorbent (Fig. 4.3). All of the sorbent has an equal opportunity to interact with the solute in solution at the same time, and the whole mixture reaches the same equilibrium at once. This process may be described by considering the sorption of a single analyte, which is shown by Eq. (4.2) as a single step process. 

Lensmeyer, G. L., Wiebe, D. A., and Darcey, B. A. 1991. Application of a novel form of solid-phase sorbent (Empore Membrane) to the isolation of tricyclic antidepressant drugs from blood, 7. Chromatog. Sci., 29 444-449. 

Polar Organic Chemical Integrated Sampler (POCIS) Portsmouth sampler using solid phase sorbents based samplers... 

Washing solid-phase sorbent with organic solvent or a mixture of solvents to remove potential interferents from SPE system... 

PUF has also been used as a solid-phase to sorb PAHs from water samples. PUF sorbents were batch-equilibrated with PAH standard solutions, removed, squeezed with a filter paper, air-dried, and subjected to solid-matrix luminescence (SML). PAH was converted to 3,4 benzopyrene for luminescence analysis. " A level of 8ngmU PAH was detected in sewage water from a petroleum refinery. More recently, cotton was applied as a solid-phase sorbent in the online investigation of tap water, sewage treatment plant effluent, and river water in Beijing, China. Water samples, of 100-ml volume and 10% 2-propanol, to prevent sorption on container walls, were preconcentrated using a precolumn attached to an HPLC-FLD system. Recoveries between 92 and 119% were reported at ngU spike levels for FLU, PHN, FLA, and B[k]F in real water samples. 

Solid-phase sorbent materials used for the extraction of amphetamines allow for high recovery and selectivity. Binding the amphetamines to the column packing material allows for washing away of the... 

PFE uses standard solvents at elevated temperatures and pressures to increase extraction efficiency. The technique uses standard laboratory solvents that would be used to extract the compound of interest, but PFE techniques use solvent near supercritical temperatures. The high pressure does not allow the solvent to boil, hence increasing its penetration, while the high temperature increases solvent viscosity. Samples are placed in stainless-steel extraction vessels that are loaded into the device, which has been programmed for the extraction protocol. Instruments are available from a variety of manufacturers who allow extraction of either a single or multiple samples. In a variant of the technique, sometimes different solid-phase sorbents are placed in the extraction vessel to allow for a more selective extraction using PFE. 

Batch extraction with solid-phase sorbents has been widely used for preffactiona-tion of biological mixtures containing small proteins and peptides [4]. The technique is inexpensive, can be applied to laige volumes, and is amenable to handling viscous samples that would plug solid-phase cartridges or analytical HPLC columns. The steps in batch extraction are listed in Table 3. 

Ionic interactions in SPE are very strong interactions. It often requires strong conditions to release analytes completely when these are bound electrostatically to the solid-phase sorbents. 

SPE can be classified by relative polarity of the solid and mobile phases. A nonpolar solid phase that preferentially associates with nonpolar or slightly polar analytes is called reversed phase, and the solvents used as eluents are polar. Normal-phase SPE employs a polar solid phase and nonpolar solvents. Highly polar and ionizable solid phases are used in ion exchange, which can also be used as a form of analysis. The continuum of solid-phase sorbents runs from reversed-phase nonpolar such as C18, through moderately polar phases such as cyanopropyl, to strong anion and cation exchangers. 

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