Matrix separation solid-phase dispersion

In matrix solid-phase dispersion (MSPD) the sample is mixed with a suitable powdered solid-phase until a homogeneous dry, free flowing powder is obtained with the sample dispersed over the entire material. A wide variety of solid-phase materials can be used, but for the non-ionic surfactants usually a reversed-phase C18 type of sorbent is applied. The mixture is subsequently (usually dry) packed into a glass column. Next, the analytes of interest are eluted with a suitable solvent or solvent mixture. The competition between reversed-phase hydrophobic chains in the dispersed solid-phase and the solvents results in separation of lipids from analytes. Separation of analytes and interfering substances can also be achieved if polarity differences are present. The MSPD technique has been proven to be successful for a variety of matrices and a wide range of compounds [43], thanks to its sequential extraction matrices analysed include fish tissues [44,45] as well as other diverse materials [46,47]. 

In our laboratory, an on-flow LC-NMR-MS screening (Figure 5.1.1) was applied to both saponin fractions which were not separated into pure compounds by classical column chromatography and further to total asterosaponin fractions obtained by the micropreparative technique, matrix solid-phase dispersion (MSPD) extraction [45] (see Figure 5.1.2). The LC-NMR-MS hyphenation is set up in the widely used parallel configuration of NMR and mass spectrometer (Figure 5.1.3). Typically, absolute amounts of asterosaponin mixtures of about 500 xg - 1 mg are injected onto the column. 

Figure 5.1.2 Matrix solid-phase dispersion (MSPD) extraction as a micro-preparative extraction technique for an on-flow LC-NMR-MS screening. Since the latter requires only sample amounts in the 0.5-2 mg range, the sample preparation can be achieved by fast small-scale extraction procedures, such as MSPD. This is a sample preparation technique that combines both sample homogenisation and extraction of compounds of interest in one single step starting from the intact sample material. Thus, it simplifies the extraction and clean-up steps, reduces the sample manipulation and is much faster than conventional techniques. It is therefore very well suited for a rough separation of extracts into classes of compounds of similar polarities, which can then be submitted to LC-NMR-MS analysis...

Fats, oils, and lipids are common components of meats, nuts, and dairy products and manufactured goods, such as potato chips, cookies, and chocolate. They are soluble in nonpolar solvents, such as hexane and methylene chloride. The analyte, of course, should also be soluble in the extraction solvent. Typically normal-phase SPE would be used to retain a compound from this extraction solvent. A solid fat may be homogenized in a blender with hexane, filtered or centrifuged, then the solvent would be passed through a normal-phase column for retention of the solute. Another approach is the use of matrix solid-phase dispersion, where the solid would be ground into the silica and C-18 directly, then the analyte eluted directly from the ground mixture with either hexane or methylene chloride. The hexane or methylene chloride extract could then be applied directly to a normal-phase sorbent for separation. Liquid oils may be directly diluted with hexane or methylene chloride and applied to the normal-phase sorbent. Other lipid substances may be handled either as solids or liquids depending on their form. 

The effects of minor proportions of PVC and PS in the polyolefins are quite dramatic. As little as 5% of PVC or PS in LDPE reduces the impact strength (toughness) of the latter by about 65%. This results from their presence as separate phases in the polyolefin matrix which leads to rapid crack propagation on impact. The effect of PP is very much less 10% of PP in LDPE reduced the energy absorbing capacity (toughness) of the matrix by only 1 % and 20% of PP reduced it by only 5%. The addition of block copolymers which act as compatibilisers or more correctly solid-phase dispersants (SPDs) for a second incompatible phase reduces the size of the heterogeneous domains and improves impact resistance. However, a considerable concentration ( 20%) of SPD is required, which unacceptably increases the cost in most cases. 

Extraction of pesticide residues from liquid samples can be performed using a solid sorbent material. Currently available sorbent extraction techniques include (1) solid-phase extraction (SPE), (2) solid-phase microextraction (SPME), and (3) stir-bar sorptive extraction (SBSE). In the case of solid samples, a liquid extraction of pesticide residues (transfer into a solution) usually precedes the sorption step thus, it should be considered rather as a clean-up than an extraction. Matrix solid-phase dispersion (MSPD) represents a unique SPE approach that combines extraction and clean-up of solid or semisolid food samples in one step. In MSPD, the sample is mixed with a sorbent (Florisil, Cig, Cg) that serves as a solid support in sample disruption and dispersion. The resulting mix is packed into a column from which the analytes are eluted while separated matrix components are retained by the sorbent. The main drawbacks of this approach comprise rather small sample sizes ( 0.5g) and a relatively high consumption of expensive sorbents. 

Xu LY, Shi H, Liang T, Feng JT, Jin Y, Ke YX, Liang XM (2011) Selective separation of flavonoid glycosides in Dalbergia odorifera by matrix solid-phase dispersion using titania. J Sep Sci 34 1347-1354... 

Liu, H., Zhang, Y., Sun, Y, Wang, X., Zhai,Y., Sun, Y, Sun, S., Yu, A., Zhang, H. Determination of the major constituents in fruit of Arctium lappa L. by matrix solid-phase dispersion extraction coupled with HPLC separation and fluorescence detection. J. Chromatogr. B 878(28), 2707-2711 (2010)... 

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. 

Another important method for photonic crystal fabrication employs colloidal particle self-assembly. A colloidal system consists of two separate phases a dispersed phase and a continuous phase (dispersion medium). The dispersed phase particles are small solid nanoparticles with a typical size of 1-1000 nanometers. Colloidal crystals are three-dimensional periodic lattices assembled from monodispersed spherical colloids. The opals are a natural example of colloidal photonic crystals that diffract light in the visible and near-infrared (IR) spectral regions due to periodic modulation of the refractive index between the ordered monodispersed silica spheres and the surrounding matrix. 

An impact modifier is a rubber phase dispersed in particulate form throughout the matrix of a polymer solid. Unlike plasticizers, the rubber particles retain their intrinsic properties as a separate phase. The glass transition temperature of the parent matrix is not lowered by the addition of an impact modifier. The rubber particles do two things to the parent matrix phase (2,3,4) they act as stress concentrators (i.e., a large strain will start in the matrix near the interface) and they enhance the multi-axiality in stress. As multiaxial tensile strength near the interface further enhances dilatation, which shortens the mechanical relaxation time, the otherwise brittle polymer solid of the matrix will undergo plastic deformation in the vicinities of the rubber particles. 

Plastic solids derive their functionality from their unique plastic nature. Three conditions are essential for plasticity (5) (1) both liquid and solid phases must be present (2) the solid phase must be so finely dispersed that the entire solid-liquid matrix can be effectively bound together by internal cohesive forces and (3) proper proportions must exist between the phases. Incorrect phase ratios adversely influence product rheology. For example, deficient solids content may result in oil separation, whereas excessive solids can cause hardness or brittleness instead of the desired viscous flow. 

Lincomycin (and to some extent the other lincosamides) is commonly mislabeled as a macrolide and as such is often included in multi-residue macrolide procedures. Honey has been the most common target matrix, because of interest in the use of lincomycin for control of foulbrood disease in bees. Extraction from honey has principally been by dissolution/dilution with aqueous solvents. Acetonitrile has been used as extractant for tissues and milk. Dispersion onto sand prior to hot-water extraction has also been used for the analysis of milk. Solid-phase " and liquid-liquid extraction have been used for clean-up. Separation is customarily achieved on reversed phase (C18) columns prior to determination by MS or MS/MS with APCI or more commonly ESI. ... 

Research has shown that the interfacial region, which is a transition phase between the continuous polymer and dispersed sieve phases, is of particular importance in successful mixed-matrix membrane formation.The type of morphology that forms at the interfacial region has a direct impact on a membrane s separation properties, and its abUity to reach the predicted Maxwell model properties. As shown in Figure 30.4, the ideal mixed-matrix membrane will exhibit both an increase in selectivity and permeability as the solid-phase volume fraction is increased, and the Maxwell model ean be used to estimate these separation properties (as discussed earlier). 

All liquid—polymer mixed-mattix membranes have liquid polymer encapsulated in the continuous polymer matrix. The long-term stabUity of these membranes for industrial gas separation processes is stUl a critical issue because of the undesirable leakage of the liquid from the membrane. To stabilize the hquid in the polymer membrane, a new type of mixed-matrix membranes, solid—hquid—polymer mixed-matrix membranes, has been developed most recentiy. The sohd, such as activated carbon impregnated with liquid polymer such as PEG, functions as a stabilizer of the hquid polymer in the continuous polymer phase. These hybrid sohd—hquid—polymer mixed-matrix membranes combine the properties of the continuous polymer phase, the dispersed sohd filler phase, and the impregnated liquid phase. 

Margarine is an example of a solid sample where the materials of interest are soluble in one solvent (in this case methanol) whereas the matrix materials, largely triglycerides, are not. As a consequence, the sample preparation procedure is relatively simple. The chromatographic separation is achieved by using the dispersive interactions between the hydrocarbon chains of the fatty acids and the hydrocarbon chains of a reversed phase. 

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