Acid Digestions of Polymers

Teyden and co-workers [58] used XRF spectrometry to determine metals in acid digests of polymers. The aqueous solutions were applied to filter paper discs. They found that recoveries of metals by the X-ray technique were 101-110% compared to 89-94% by chemical methods of analysis. 

A concentrated nitric acid - perchloric acid - sulfuric acid digest of the polymer is analysed at 193.7 nm by atomic absorption spectrometry. The procedure is calibrated against standards of arsenic free acrylic fibre and pure arsenic trioxide. 

Starch is a polysaccharide found in many plant species. Com and potatoes are two common sources of industrial starch. The composition of starch varies somewhat in terms of the amount of branching of the polymer chains (11). Its principal use as a flocculant is in the Bayer process for extracting aluminum from bauxite ore. The digestion of bauxite in sodium hydroxide solution produces a suspension of finely divided iron minerals and siUcates, called red mud, in a highly alkaline Hquor. Starch is used to settle the red mud so that relatively pure alumina can be produced from the clarified Hquor. It has been largely replaced by acryHc acid and acrylamide-based (11,12) polymers, although a number of plants stiH add some starch in addition to synthetic polymers to reduce the level of residual suspended soHds in the Hquor. Starch [9005-25-8] can be modified with various reagents to produce semisynthetic polymers. The principal one of these is cationic starch, which is used as a retention aid in paper production as a component of a dual system (13,14) or a microparticle system (15). 

Feedstuffs consist largely of complex polymers (e.g. proteins, starches, fats) that must be hydrolyzed to the constituent building blocks before they can be absorbed and made available to the host. The digestibility of many plant proteins is inherently lower compared to proteins from animal tissues. This is particularly true for the structural proteins (Carbonaro et al, 2000 Mariotti et al, 1999). As a consequence, amino acid scores for many plant proteins often do not reflect true availability to the host (Mariotti et al, 2001). 

While additive analysis of polyamides is usually carried out by dissolution in HFIP and hydrolysis in 6N HC1, polyphthalamides (PPAs) are quite insoluble in many solvents and very resistant to hydrolysis. The highly thermally stable PPAs can be adequately hydrolysed by means of high pressure microwave acid digestion (at 140-180 °C) in 10 mL Teflon vessels. This procedure allows simultaneous analysis of polymer composition and additives [643]. Also the polymer, oligomer and additive composition of polycarbonates can be examined after hydrolysis. However, it is necessary to optimise the reaction conditions in order to avoid degradation of bisphenol A. In the procedures for the analysis of dialkyltin stabilisers in PVC, described by Udris [644], in some instances the methods can be put on a quantitative basis, e.g. the GC determination of alcohols produced by hydrolysis of ester groups. 

TXRF is most applicable to liquid samples, but success has also been achieved with direct analysis of some solids, e.g. very thin sections of organic tissue and polymer film. Alternatively, small amounts of solid material can be analysed by TXRF after acid digestion. 

The method of Kato and Nakai (27) for determining protein surface hydrophobicity was adapted for evaluating procyanidin binding to BSA and Gl. The procedure is based on the fact that the fluorescence quantum yield of cis-parinaric acid increases 40-fold when cis-parinaric acid enters a hydrophobic environment from a hydrophilic environment. The digestion of BSA by trypsin in the presence of procyanidin dimer, procyanidin trimer and black bean procyanidin polymer was evaluated by discontinuous sodium dodecyl sulfate (SDS) slab gel electrophoresis and a picryl sulfonic acid (TNBS) assay (28). 

Retention of viscous purulent secretions, which contain high concentrations of extracellular DNA—released by degenerating leukocytes that accumulate in response to infection [24]—in the airways contributes both to reduced pulmonary function and to exacerbations of infection [24,25], Digestion of DNA polymers in purulent secretion with DNAse (dornase-a or Pulmozyme) has been shown to reduce sputum viscosity in cystic fibrosis patients. The availability of recombinant DNAse has allowed its use in an aerosol formulation to deliver the enzyme into the deep lung alveoli of CF patients. The purihed glycoprotein contains 260 amino acids with an approximate molecular weight of 37,000 daltons [26], The primary amino-acid sequence is identical to that of the... 

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