Ether sulfates characterization

Thin-layer chromatography (TLC) is used both for characterization of alcohol sulfates and alcohol ether sulfates and for their analysis in mixtures. This technique, combined with the use of scanning densitometers, is a quantitative analytical method. TLC is preferred to HPLC in this case as anionic surfactants do not contain strong chromophores and the refractive index detector is of low sensitivity and not suitable for gradient elution. A recent development in HPLC detector technology, the evaporative light-scattering detector, will probably overcome these sensitivity problems. 

A wide range of anionic surfactants (Fig. 23) has been classified into groups, including alkyl benzene sulfonates (ABS), linear alkyl benzene sulfonates (LAS), alcohol sulfates (AS), alcohol ether sulfates (AES), alkyl phenol ether sulfates (APES), fatty acid amide ether sulfates (FAES), alpha-olefin sulfates (AOS), paraffin sulfonates, alpha sulfonated fatty acids and esters, sulfonated fatty acids and esters, mono- and di-ester sulfosuccinates, sulfosuccinamates, petroleum sulfonates, phosphate esters, and ligno-sulfonates. Of the anionic surfactants, ABS and LAS continue to be the major products of anionic surfactants [314, 324]. Anionic surfactants have been extensively monitored and characterized in various environmental matrices [34,35,45,325-329]. 

Thus these characterization results not only give the distribution of the acrylic acid between the aqueous serum, particle surface, and particle interior, but also account satisfactorily for the total number of strong-acid groups arising from the anionic emulsifier and initiator. In addition, both the sodium lauryl ether sulfate and the nonylphenol polyoxyethylene adduct used in the polymerization were recovered from the fractions obtained by serum replacement. 

The alcohols can be oxidized to the corresponding acids. Guerbet alcohols, acids, their esters, sulfates, and ether sulfates are used as lubricants, cosmetic additives, and surfactants. Their synthesis, characterization, and applications have been reviewed (93). 

V. Bernabe-Zafon, S. Ortega-Gadea, E.F. Sim6-Alfonso and G. Ramis-Ramos, Characterization and quantitation of mixtures of alkyl ether sulfates and carboxylic acids by capillary electrophoresis with indirect photometric detection. Electrophoresis, 24, 2805-2813, 2003. 

It is only a small step from the alkyl sulfates to the so-called alkyl ether sulfates. These surface-active agents are made from alcohols which are ethoxylated. The formed fatty alcohol polyglycol ethers possess a final OH-group which then reacts with sulfuric acid. Fatty alcohol polyglycol sulfates are characterized by an insensitivity to water hardness and low irritation of the skin. Their aqueous solutions can be easily thickened by the addition of sodium chloride. These properties thus attract attention for the use of fatty alcohol polyglycol sulfates in cosmetic products. 

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. 

Ether sulfates may contain low levels of 1,4-dloxane, both because of impurities in the starting ethoxylate and because of formation of dioxane during the sulfation reaction (79). This analysis is discussed with the characterization of nonionic surfactants (Chapter 2). 

Henrich developed a comprehensive TLC method for identification of surfactants in formulations (4). She specified two reversed-phase and four normal phase systems, with detection by fluorescence quenching, pinacryptol yellow and rhodamine B, and iodine. Prior to visualization, one plate was scanned with a densitometer at 254 nm, and UV reflectance spectra were recorded for each spot detected. Tables were prepared showing the Rf values of 150 standard surfactants in each of the six systems, along with the reflectance spectra and response to the visualizers. This system allows for systematic identification of compounds of a number of surfactant types (LAS, alcohol sulfates and ether sulfates, alkane sulfonates, sufosuccinate esters, phosphate compounds, AE, APE, ethoxylated sorbi-tan esters, mono- and dialkanolamides, EO/PO copolymers, amine oxides, quaternary amines, amphoterics and miscellaneous compounds). Supplementary analysis by normal phase HPLC aided in exactly characterizing ethoxylated compounds. For confirmation, the separated spots may be scraped from one of the silica gel plates and the surfactant extracted from the silica with methanol and identified by IR spectroscopy. 

Preparation of 4-12-cvclohexenvloxv )-stvrene. A stirred mixture of 34.36g (0.096 mole) methyltriphenylphosphonium bromide and 10.75g (0.096 mole) potassium t-butoxide in 200ml dry THF is treated drop-wise with a solution of 16.16g (0.080 mole) of 4-(2-cyclohexenyl)-benzaldehyde in 30ml THF under inert atmosphere. Once the addition of aldehyde was completed, the mixture was stirred at room temperature for another 2 hours. Ether and water were then added to the reaction mixture until clearly separated phases were obtained with no solid residue. The organic layer was separated and washed three times with water, dried over magnesium sulfate and evaporated. The resulting semi-solid was triturated in 10% ethyl acetate-hexane mixture to remove most of the triphenylphosphine and the evaporated extract was purified by preparative HPLC using hexane as eluent. This afforded 9.35g (58%) of the pure monomer, which was fully characterized by H and C-NMR as well as mass spectrometry. 

Alcohol (5 mmol), catalyst 1 (5 mol %, 84 mg) and TEMPO (5 mol %, 39 mg) were stirred at ca. 100 °C in toluene (10 mL) under atmospheric oxygen for the appropriate time (Table 5.1). After completion, the reaction mixture was treated with water (3 mL) and the organic layer, after drying over sodium sulfate and GC analysis, was passed through a short pad of sihca gel using ethyl acetate (or diethyl ether) and hexane as an eluent to provide the analytically pure aldehyde which was characterized by NMR, IR and mass analysis. 

Mixtures of methyl ethers result from the treatment of myo-inositol with dimethyl sulfate and alkali. Although none of these mixtures have been adequately characterized, pure (or seemingly pure) compounds which have been isolated from them include the monomethyl ether166 (later identified... 

Methylenedioxyphenylacetic acid (18.0 g) was added portion wise over 30 minutes to a stirred, ice-cooled suspension of lithium aluminium hydride (4.0 g) in ether (400 ml) and the mixture was stirred at temperature for two hours, quenched by the cautious addition of saturated aqueous ammonium chloride solution and filtered. The filtrate was washed with 10% aqueous sodium carbonate solution, dried over magnesium sulfate and evaporated to give the title compound as a pale yellow oil (15.01 g, 90%), which was characterized by its tH-NMR spectrum. 

The first chemical work on calabash curare was carried out in 1897 by Boehm (8), who isolated a highly active amorphous material which was named curarine. This was soluble in water and insoluble in ether, so it is probable that Boehm was handling a mixture of crude quaternary alkaloids. Much later (1935), King described (9) the preparation of an equally active amorphous quaternary iodide from the bark of S. toxifera. However, the first isolation of well-characterized crystalline alkaloids was achieved by H. Wieland and his school (10-13). Calabash curares were extracted with methanol, and the water-soluble quaternary alkaloids in the extract were precipitated as the reineckate salts this mixture was then fractionated by adsorption chromatography on alumina. The various reineckate fractions so obtained were converted into the corresponding chlorides by successive treatment with equivalent quantities of silver sulfate and barium chloride some of the quaternary alkaloids then crystallized as the chlorides or as the picrates. C-Curarine1... 

A typical reaction procedure was as follows a mixture of zeolite (5 g) and amide (10 mmol) in an appropriate solvent (25 ml) was vigorously stirred under reflux at 75°C (using a thermostated bath) under nitrogen atmosphere. The reaction was periodically monitored by GLC. At the end of the reaction, the mixture was filtered and the cake washed with methanol and diethyl ether. After drying with anhydrous sodium sulfate, the solvent was evaporated and the residue purified by distillation or crystallization. The known compounds were characterized by their GC/MS spectra, as well as by their melting points or boiling points, by comparison with standards. 

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