A gas chromatographic method for the determination of aldose and uronic Acid constituents of plant cell wall polysaccharides

A major problem in determining the composition of plant cell wall polysaccharides has been the lack of a suitable method for accurately determining the amounts of galacturonic and glucuronic acids in such polymers. A gas chromatographic method for aldose analysis has been extended to include uronic acids. Cell wall polysaccharides are depolymerized by acid hydrolysis followed by treatment with a mixture of fungal polysaccharide-degrading enzymes. The aldoses and uronic acids released by this treatment are then reduced with NaBH(4) to alditols and aldonic acids, respectively. The aldonic acids are separated from the alditols with Dowex-1 (acetate form) ion exchange resin, which binds the aldonic acids. The alditols, which do not bind, are washed from the resin and then acetylated with acetic anhydride to form the alditol acetate derivatives. The aldonic acids are eluted from the resin with HCl. After the resin has been removed, the HCl solution of the aldonic acids is evaporated to dryness, converting the aldonic acids to aldonolactones. The aldonolactones are reduced with NaBH(4) to the corresponding alditols, dried and acetylated. The resulting alditol acetate mixtures produced from the aldoses and those from the uronic acids are analyzed separately by gas chromatography. This technique has been used to determine the changes in composition of Red Kidney bean (Phaseolus vulgaris) hypocotyl cell walls during growth, and to compare the cell wall polysaccharide compositions of several parts of bean plants. Galacturonic acid is found to be a major component of all the cell wall polysaccharides examined.

Moisture uptake and tensile strength of bulk solids

An apparatus is described in which bulk solid handling properties can be examined over a wide range of humidities. It is shown that constant temperature and relative humidity can be maintained. The apparatus can also be used to study the effect of cycles of humidity changes. The rate of moisture uptake by loosely packed and tapped beds of six pharmaceutical materials was found to be dependent upon bed depth but independent of bulk density. The tensile strengths of the bulk solids changed when they were subjected to high relative humidities.

The flow of granular magnesia

Investigations of the flow rates of loosely packed magnesia have shown that the general equation developed by Jones & Pilpel (1966)

can be applied to single component and multicomponent mixtures in the size range 0·003 to >0·2 cm. The increase in flow rate caused by mixing coarse and fine particles has been related quantitatively to the size of the particles by the general expression

This can be used to calculate the composition for maximum flow in multicomponent mixtures. The mechanism of action of glidants is discussed in the light of the experimental results and a distinction is made between glidants which improve the flow of granulations and those which improve the flow of cohesive powders.

The flow properties of granular magnesia

Measurements have been made of the flow of granular magnesium oxide through circular orifices and the equation

has been derived. This is a particular form of a more general equation

which can be shown to apply to a wide range of materials, A and 1/n being functions of particle size and shape.

The equation has been employed for predicting the flow rates of binary and ternary mixtures of magnesia with an accuracy of 5%.

Some physical properties of lactose and magnesia

Anomalies in some of the physical properties of spray dried lactose and granulated magnesium oxide have been traced to the presence of fines. These are strongly adsorbed onto particles of about 1,000 μ diameter, being held in position by van der Waals’ and electrostatic forces. Although they are not displaced during sieving, they can be removed by washing the powders with organic solvents.