Determination Of Acetyl Groups Research Articles

Hot-water extraction of ground spruce wood of different particle size

Hot-water extraction of hemicelluloses, especially galactoglucomannans, from fractions of ground spruce wood with different particle sizes was studied at 170°C with extraction times up to 60 min. Extraction of spruce sapwood, heartwood, and thermomechanical pulp (TMP) was also compared at 160 to 180°C. Static batch extractions were carried out in an accelerated solvent extractor (ASE). The extracted hemicelluloses were characterized by sugar unit analysis and determination of acetyl groups and molar masses. The particle size significantly affected the extraction of ground wood. The total extraction yield, as well as the yields of hemicelluloses and monosaccharides, was the highest from the finest ground wood fraction (< 0.1 mm). The release of acetic acid, average molar mass of extracted hemicelluloses, and end-pH of the extracts were also dependent of the particle size, although to a lower extent. Irrespectively of the ground wood particle size, the yield of hemicelluloses reached a plateau after 40 min extraction at 170°C. The results indicate that extraction of hemicelluloses is limited mainly by the diffusion in the fiber wall, and for coarse wood shives also by the mass transfer in the wood matrix. There were only small differences in the hot-water extraction yields of hemicelluloses from spruce sapwood, heartwood, and TMP, considering both poly- and monosaccharides.

Chemische Charakterisierung von thermisch belastetem Holz: Bestimmung des Acetylgruppengehalts und FTIR-Spektroskopie

Thermically treated and untreated samples of various commercial woods were analysed for chemical changes during treatment. Besides FTIR-spectroscopy, quantitative determination of acetyl groups was performed.

A specific micromethod for determination of acetyl residues in proteins

A sensitive, specific, and economical method for the detection and determination of acetyl groups in proteins and other biochemical substances is described. It is based on the utilization of acetate kinase, pyruvate kinase and lactate dehydrogenase. An amount of acetate as low as 0.02 μmole/ml can be detected and determinated quantitatively. The application of this method to rabbit muscle phosphofructokinase revealed that this enzyme contained one acetyl group per 62,000 g. The latter figure is probably the molecular weight of the subunit of phosphofructokinase. The possible significance of this structural characteristic is discussed.

Submicro methods for the analysis of organic compounds : The determination of acetyl groups

Methods are described for the determination of O-acetyl and N-acetyl groups in 30–80-μg samples of organic compounds. The best general method involved hydrolysis with Wenzel sulphuric acid and distillation of the acetic acid formed, in a small apparatus of the wiesenberger type, followed by visual acid-base titration. The overall recovery was 99.1% and the average relative accuracy was ± 2.5% ; accuracy and precision were slightly less satisfactory for alkaline hydrolysis or hydrolysis with phosphoric acid.

Some studies in the microanalytical determination of acetyl groups

Experience with theSchoniger, Lieb andEl Din Ibrahim apparatus for acetyl and C-methyl determinations has confirmed the authors' claims that it gives a simple, rapid and quantitative distillation of acetic acid. It is shown that the 1N methyl alcoholic sodium hydroxide reagent is not as effective as has been thought hitherto and that 5N sodium hydroxide in methyl alcohol (33 per cent) is a more effective and versatile reagent for acetyl determinations.

The determination of acetyl groups by trans-esterification

The determination of acetyl groups by trans-esterification