Ester ethoxylates separation

The amount of residual sulfonate ester remaining after hydrolysis can be determined by a procedure proposed by Martinsson and Nilsson [129], similar to that used to determine total residual saponifiables in neutral oils. Neutrals, including alkanes, alkenes, secondary alcohols, and sultones, as well as the sulfonate esters in the AOS, are isolated by extraction from an aqueous alcoholic solution with petroleum ether. The sulfonate esters are separated from the sultones by chromatography on a silica gel column. Each eluent fraction is subjected to saponification and measured as active matter by MBAS determination measuring the extinction of the trichloromethane solution at 642 nra. (a) Sultones. Connor et al. [130] first reported, in 1975, a very small amount of skin sensitizer, l-unsaturated-l,3-sultone, and 2-chloroalkane-l,3-sultone in the anionic surfactant produced by the sulfation of ethoxylated fatty alcohol. These compounds can also be found in some AOS products consequently, methods of detection are essential. 

If a sorbitan ester and a sorbitan ester ethoxylate are present as separate components, they can be determined provided the degrees of ethoxylation and esterification are known. 

Fatty alcohol- (or alkyl-)ethoxylates, CoE, are considered to be better candidates for LLE based on their ability to induce rapid phase separation for Winsor II and III systems. (Winsor III systems consist of excess aqueous and organic phases, and a middle phase containing bicontinuous microemulsions.) However, C,E,-type surfactants alone cannot extract biomolecules, presumably because they have no net negative charge, in contrast to sorbitan esters [24,26,30,31]. But, when combined with an additional anionic surfactant such as AOT or sodium benzene dodecyl sulfonate (SDBS), or affinity surfactant, extraction readily occurs [30,31]. The second surfactant must be present beyond a minimum threshold value so that its interfacial concentration is sufficiently large to be seen by... 

Ethoxylated sorbitan ester surfactant mixtures like Tween 20 (cf. Fig. 2.9.38) were often used in biochemical applications. Detergents of this type were analysed by MALDI MS. The aim was to compare the separation results of TLC and RP-LC and to detect impurities within these ethoxylated sorbitan esters [30], Tween 20, the ethoxylated sorbitan carboxylate was ionised resulting in [M + Na]+ and [M + K]+ ions. The Tween 20 isomeric and homologue molecules contained a varying number of ethoxylate units. The number of EO units (-CH2CH2O-) was determined from 18 to 34 resulting in Am/z 44 equally spaced signals [30]. 

A reduction in the corrosive action of water is an extremely important property of surfactants. The mechanism of this phenomenon has been presented in a work by Somasundaran and Huang [89], The authors assume that the adsorbed film formed at the interface efficiently separates the water from the metal surface. Experiments confirming the anticorrosive action of surfactants have been presented in several works [90-94]. The following compounds were used in the experiments as additives cationic surfactants (cetyl pyridinium chloride and trimethyl ammonium bromide) [89], ethoxylated fatty acids [90], ethoxylated fatty alcohols [91], and ethoxylated sorbitan esters [92-94]. 

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. 

Ether carboxylates. Ether carboxylates are readily analyzed as the methyl esters. Separation of NPE carboxylate has been demonstrated up to a degree of ethoxylation of about 7 (36). 

Alkanesulfonate hydrotropes fatty alcohol sulfate alkylbenzenesulfonate sulfated fatty alcohol ethoxylate (homologs are separated) soap a-sulfo fatty acid methyl ester sulfosuccinic acid diesten qualitative... 

Cy alkyl ester of PEG separation of PEG, monoester, diester single peak for each Mono- and dioleate of 10-mole ethoxylate of N,N -his (2-hydroxyethyl)-5,5-dimethyl-hydantoin preparative separation of mono- and diester and free ethoxylate Mono- and di-heptanoate of tetraethylene glycol determination of mono- and diester, heptanoic acid, and tetraethylene glycol... 

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