Tissue matrix

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. 

On-line dialysis also separates the analyte from tissue matrix based upon molecular size, but in this case, the sample extract is passed over a membrane filter through which the analyte (and other low molecular weight compounds) is diffused into a second solvent on the other side of the membrane filter. Usually, the second solvent is then concentrated on to an SPE column to minimize the dilution effect that is caused by the dialysis process. Agasoester used on-line dialysis to separate oxytetracycline from muscle, liver, milk, and egg tissue matrix components. A problem encountered with on-line dialysis is the inability of analyte molecules that are bound to proteins in the sample extract to pass through the membrane filter. Problems with membrane clogging are reduced with on-line dialysis compared with ultrafiltration because no external force is being applied to bring the analyte across the membrane filter. 

Oily crops such as soybeans and canola (oilseed rape) cannot be extracted with aqueous buffers, because the extraction solvent cannot permeate the hydrophobic plant tissue matrix. In these cases, homogenization in acetonitrile-hexane is recommended. This solvent mixture is able to extract sulfonylureas from these samples with a minimum of co-extracted oil. After extraction, the sulfonylureas partition into the acetonitrile phase while most of the oil stays in the hexane phase. Further cleanup is accomplished using a silica SPE cartridge and normal-phase conditions. 

Weigh 20 g of homogenized sample into a 300-mL tail-form beaker. Begin recovery samples at this point by fortifying the control tissue matrix samples. Add 120 mL of acetone, and homogenize the mixture for approximately 5 min followed by the addition of 60 mL of laboratory-grade water with another 2 min of homogenization. 

Weigh 5.0 g of frozen homogenized sample into a 120-mL tail-form glass bottle. Begin recovery samples at this point by fortifying the control tissue matrix samples. 

A prime determinant of the absorption rate from an SC injection is the total surface area over which the absorption can occur. Although the subcutaneous tissues are somewhat loose and moderate amounts of fluid can be administered, the normal connective tissue matrix prevents indefinite lateral spread of the injected solution. These barriers may be overcome by agents that break down mucopolysaccharides of the connective tissue matrix the resulting spread of injected solution leads to a much faster absorption rate. 

The skin consists of two main compartments, the epidermis, a stratified squamous epithelium, and the underlying dermis, a richly vascularized tissue embedded in a connective tissue matrix (Fig. 41.1). The epidermis consists of multiple layers of keratinocytes, which differentiate into the outermost layer, the stratum corneum. This layer contains the hydrophilic structural... 

Chapman JA, Hulmes DJS (1984) In Ruggeri A, Motta PM (eds) Ultrastructure of the Connective Tissue Matrix, Martinus Nijhoff, Boston 1984, Chapter 1, Fig 1... 

The sample is disrupted completely and distributed over the surface as a function of interactions with the support, the bonded phase, and the tissue matrix components themselves. The solid support acts as an abrasive that promotes sample disruption, whereas the bonded phase acts as a lipophilic, bound solvent that assists in sample disruption and lysis of cell membranes. The MSPD process disrupts cell membranes through solubilization of the component phospholipids and cholesterol into the Cis polymer matrix, with more polar substituents directed outward, perhaps forming a hydrophilic outer surface on the bead. Thus, the process could be viewed as essentially turning the cells inside out and forming an inverted membrane with the polymer bound to the solid support. This process would create a pseudo-ion exchange-reversed-phase for the separation of added components. Therefore, the Cis polymer would be modified by cell membrane phospholipids, interstitial fluid components, intracellular components and cholesterol, and would possess elution properties that would be dependent on the tissue used, the ratio of Cis to tissue employed and the elution profile performed (99-104). 

However, recent investigations on the effect of the tissue matrix on the detection limits attained by this test have indicated that ceftiofur, sulfonamides, streptomycin, and some macrolide antibiotics cannot be detected in intact meat with the plates and the bacterial strains prescribed in the European four-plate test (81, 82). Two plates of this system were not found suitable for screening sulfamethazine or streptomycin at levels far above the MRL the third plate detected tetracyclines and -lactams up to the MRL levels whereas the fourth was sensitive to -lactams and some but not all macrolides. Detection, on the other hand, of the fluoroquinolones enrofloxacin and ciprofloxacin could only be made possible by an additional Escherichia coli plate not included in the four-plate test. 

Diethylstilbestrol is particularly difficult to quantitate below 1.0 ppb in bovine tissues, especially in liver, which is among the last tissues to contain diethystilbestrol after cattle are withdrawn from receiving tire drug (101, 102). Interferences from tissue matrix constitute a major problem that might be due to nonspecific interference of lipids and fatty compounds (103, 104). In addition, problems with false-positive results often appear in urine analysis unless a chromatographic step such as a solid-phase extraction cleanup (105, 106) is introduced. Simple sample preparation procedures such as those based on solvent extraction and liquid-liquid partitioning do not usually give satisfactory results (107, 108). 

Hukins, D. W. L. (1984) Connective Tissue Matrix, MacMillan, New York... 

A multiresidue technique—matrix solid-phase dispersion (MSPD)—was used to purify the meat samples. The prewashed Cl8 bulk material was gently ground with the blended sample. The resultant C18/tissue matrix mixture was transferred to a 10-ml syringe barrel. The precolumn prepared in this way was washed with hexane, and FZD residues were eluted with dichloromethane, with 13 other veterinary drugs assayed. The recoveries varied from 44% to 87%, depending on the concentration level, and the LOD was established at 2.5 ng/kg (20). 

Parry, D. A. D., and Craig, A. S. (1984). Growth and Development of Collagen Fibrils in Connective Tissues. In Ultrastructure of the Connective Tissue Matrix (A. Ruggeri and P.M. Motta, Eds.), pp. 34-64. Martinus Nijhoff, Netherlands. 

Kumar, R. Sivaraman, N. Srinivasan, T.G. VasudevaRao, RR. Studies on the supercritical fluid extraction of uranium from tissue matrix, Radiochim. Acta 90 (2002) 141-145. 

Living tissue is a nonideal matrix for spectroscopy. The transmission of light through living tissue is complicated by numerous phenomena related to complex interactions between the propagating light with the heterogeneous nature of the tissue matrix. 

By definition, the residual spectmm determined from the pure component glucose spectmm is the NAS for glucose in this particular tissue matrix.35 As described above, the NAS corresponds to the orthogonal component of the glucose absorption spectmm relative to the nonglucose-dependent spectral variance. 

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