Analysis of ethers

In comparison with other anionics, little has been published concerning methods of analysis of ether carboxylates. Gerhardt et al. [238] investigated the analytical determination of ether carboxylic acids in reaction mixtures obtained by reaction of nonylphenol ethoxylates with sodium chloroacetate as well as by cyanoethylation by different methods. Several methods, used for other surfactants as well [239], can be used for ether carboxylates. 

Mengerink et al. [243] describe for the analysis of ether carboxylic acids and mixtures thereof with ethoxylated alcohols an HPLC method with the use of a evaporative light-scattering detector (ELSD). 

Mangold, H. K. and Totani, N. (1983) Procedures for the analysis of ether lipids, in Ether Lipids. Biochemical and Biomedical Aspects, H. K. Mangold, and F. Paltauf, editors, Academic Press, New York, pp. 377-387. 

Figure 5. DSC analysis of ether extract from A newborn rat stratum corneum and B human hair (N2 atm). Data from Ref. 18.

The same dilution technique is usually applied in the analysis of ethereal oils [210]. It can be used in the determination of aldehydes such as citral and citronellal in lemon oil (Oleum citri) and in Oleum verbenae, of anisaldehyde in Oleum anisi stellati. Oleum anisi and Oleum foeniculi, of cinnamaldehyde in Oleum cinnamomi, and of ketones, such as car-vone, in Oleum anethi, of pulegone and diosphenol. In all these cases, the oil is first diluted with ethanol and to this solution an aqueous solution of the supporting electrolyte is added, usually only 0.1 M LiCl. 

Blank, M.L., Snyder, F. 1994. Chromatographic analysis of ether-linked glycerolipids, including plateletactivating factor and related cell mediators. In lipid Chromatographic Analysis. T. Shibamoto, editor. New York, NY Marcel Dekker, pp. 291-316. 

The most characteristic feature in the spectroscopic analysis of ethers is the strong band of C-0 stretching. It occurs in the 1060-1300 cm range. In this region, many bands are present, but this alone does not establish the presence of an ether. For note, alcohols, carboxylic acids, and esters also show C-0 stretching. They can be eliminated as possibilities, however, by the fact alcohols would also show the strong and broad 0-H stretch in the 3200-3600 cm , car-... 

Table I. Compositional Analysis of Ether-Solubles from the Aqueous Phase ...

Qualitative and quantitative analysis of ethereal oils is usually aehieved by gas-ehromatography (GC), and the eombination of this method of separation with mass speetrometry (GC-MS) for identifieation. Pure terpenes are obtained on a larger scale from ethereal oils by distillation ehromatographie methods of separation predominantly in the gas (GC) or liquid phase (LC) permit the isolation of small amounts with high purities. 

It is now known that, although complete hydrolysis of the vinyl ether bond occurs with this method, only 80% recovery of aldehydes is likely to be attained, although these are probably representative in composition of the alk-1-enyl moieties originally present in the natural compound [992]. Addition of an odd-chain aldehyde to the reaction medium for use as an internal standard will correct for a proportion of these losses. Generation of aldehydes can also be effected as part of a more comprehensive scheme for the analysis of ether lipids (see below). 

Noninstramental analysis of ether sulfates is complex because of the various types of organic material which must be distinguished. Puschmaim and Wickbold have described comprehensive procedures for quantitative determination of the components in alkyl ether sulfates by wet chemical methods (68,69). Nowadays, these tests are usually performed by HPLC. Cloud point determination, a measure of EO content, is described in Chapter 2 with characterization of nonionic surfactants. 

Gerhardt, W., G. Czichocki, H.-R. Holzbauer, C. Martens, B. Weiland, Synthesis and analysis of ether carboxylic acids. Characterization of ether carboxylic acids during the synthesis process (in German), Tenside, Surfactants, Deterg., 1992,29, 285-288. 

TABLE 3 HPLC Analysis of Ether Sulfate Surfactants... 

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