Cellulose matrix substance

The test is based on an ion-selective reaction. The reaction takes place in a cellulose matrix into which an organic phase and the substances of the aqueous phase have been incorporated. If a sample is applied, the aqueous phase reconstitutes itself. The potassium-selective ionophore mediates the transport of the potassium ion from the aqueous phase to the organic phase. The neutrality of charge of the organic phase is ensured by the simultaneous loss of a proton by the indicator dye. The release of a proton results in a change of the absorption of the dye that can be measured at 640 nm at intervals of 5 seconds by measuring the reflectance. The result is displayed after 45 seconds. 

The wood cell consists mainly of cellulose, hemicelluloses, and lignin (see Appendix). A simplified picture is that cellulose forms a skeleton which is surrounded by other substances functioning as matrix (hemicelluloses) and encrusting (lignin) materials. 

This is based on the partitioning of a substance between two liquid phases, in this instance the stationary and mobile phases. Substances which are more soluble in the mobile phase will pass rapidly through the system while those which favour the stationary phase will be retarded (Fig. 31.2). In normal phase partition chromatography the stationary phase is a polar solvent, usually water, supported by a solid matrix (e.g. cellulose fibres in paper chromatography) and the mobile phase is an immiscible, non-polar organic solvent. For reversed-phase partition chromatography the stationary phase is... 

As mentioned earlier, the initial portion of a fiber cell wall is manufactured in the cambial zone and is referred to as the primary wall. Here, cellulose microfibrils form a random, irregular, and interwoven network (Figure 17) to facilitate cell expansion during the enlargement phase of fiber development. In addition to cellulose, the primary wall contains a large proportion of matrix carbohydrates, particularly pectic materials and hemicelluloses see Chapter 2). The combination of two adjacent primary walls and the interdisposed true middle lamella zone is collectively referred to as the compound middle lamella. Microscopically, it is difficult to separate wall substance here from the interfiber substance. 

As the main component, it provides the actual matrix to which lipophilic or water-insoluble substances such as stearic acid and stearyl alcohol [475-476], cellulose derivatives [476], starch [475] or calcium hydrogen phosphate [474] are added. 

Examples of successful fractionations of aquatic humic substances where only one fractionation mechanism was operative include utilization of the hydrophobic properties of XAD resins (Mantoura and Riley, 1975 Aiken et al., 1979), hydrogen bonding of weak-acid functionalities of humic constituents to weak-base anion-exchange resins (Kim et al., 1976), and use of ion-exchange celluloses for ion-exchange fractionation of aquatic humic substances without hydrophobic matrix adsorption (Sirotkina et al., 1974). These examples of successful fractionations demonstrate the potential for chromatography of aquatic humic substances when fractionations are designed carefully to avoid undesirable interactions. 

In contrast to the cell walls of parenchymatous tissues of dicotyledons, those of cereal grains (wheat, barley, etc.) contain very little, or no, pectic substances. The primary walls of most cereal grains have cellulose microfibrils, which are closely associated with glucomannan, and these fibrillar structures are embedded in an amorphous matrix of hemicelluloses, which consists mainly of arabinoxylans and/or P-D-glucans, some of which are cross-linked by phenolic esters and/or proteins (Selvendran,... 

The authors stated (8) that the middle lamella and the matrix of the cell wall is effected by chemical changes such as oxidation and hydrolysis to a higher extent than the cellulose microfibrils. Ultrastructural changes would then be expected to occur in areas rich in hemicelluloses, lignin, or pectic substances. Later, Borgin et al. (10) found that the lignin in the ancient wood samples had been oxidized. A decrease in lignin content was evident when the samples were analyzed by a hydrochloric acid procedure. 

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