Zeisel procedures

Anderson and co-workers [5] used combined Zeisel reaction chromatography and GC to analyse acrylic copolymers. Acrylic esters were cleaved with hydriodic acid and gas chromatography was used for analysing the alkyl iodides so formed  

Using this procedure, the recovery of alkyl iodides is greater than 95% for polymers containing between 10 and 90% of the methyl, ethyl, and butyl esters of acrylic and methacrylic acid. In addition, the use of isopropylbenzene as the trapping solvent allows the determination of all Cj to alkyl iodides. 

Results obtained by applying this method to a range of acrylic polymers gave recoveries greater than 95% for polymers containing between 10 and 100% acrylic monomer. The method has 99% confidence interval of 0.8. The presence of comonomers such as styrene, acrylonitrile, vinyl acetate, acrylamide, or acrylic acid does not change the recovery of acrylate or methacrylate esters. Non-quantitative results are obtained, however, for polymers containing hydroxypropyl methacrylate. 

The Ziesel reaction has been used for the determination of alkoxyl groups in cellulosic materials [6,7] and the determination of ether groups in cellulose and polyvinyl ethers 

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Methoxyl content of the different samples were determined using a modified Zeisel procedure (14). 

We have already discussed the cleavage of ethers by acids (Sec. 17.7). Cleavage of methyl aryl ethers by concentrated hydriodic acid is the basis of an important analytical procedure (the Zeisel procedure See. 17.16). 

The purity of a lignin sample can, in many cases, be judged based on the methoxyl content. The methoxyl content is nsnally determined according to modihed Zeisel procedures [123], Alternatively the methoxyl content can be determined by NMR spectroscopy [124], The methoxyl content can also be roughly estimated based on H NMR spectral examinations [79],... 

Holden84 used a method of measurement in which the methanol liberated by PM in a buffered solution of pectinic acid in ten minutes has been estimated by the Zeisel method. This procedure is much more complicated than that described above and must be regarded as unreliable on account of the rapid change in the pH of such reaction mixtures, even if buffered. 

The determination of the methoxy group (OCH ) content of soils is important in studies concerned with the degree of humification of soil organic matter. Methods used to determine methoxy groups in soils have generally been based on volumetric modifications of the classical Zeisel method, which is a complicated and tedious procedure requiring specialised apparatus. 

This Section Ls restricted to a description of some of the work of Ander-gon, 8-a> who has ably applied the quantitative analysis of vapors by infrared spectroscopy to analytical problems in carbohydrate chemistry, principally to the Zeisel alkoxyl determination. In this particular application, the usual Zeisel apparatus was used, and the volatile iodide liberated was carried by a flow of nitrogen into a cold trap where it was collected quantitatively Anhydrone (magnesium perchlorate) was used for removing water vapor which would otherwise interfere in the spectrum. The contents of the trap were allowed to vaporize into an evacuated gas-cell, and air was then admitted through the trap to sweep all the vapor into the gas-cell. Double-beam compensation of atmospheric water vapor and carbon dioxide was not upset by this procedure, which also served the purpose of increasing the sensitivity of the infrared method by the well known pressure-broadening effect. The complete spectrum of the vapor... 

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