Amphoteric ions surfactants

Amphoteric surfactants are ionic surfactants containing positive and negative charges on the same molecule [7]. They can be true amphoteric ions, such as the betaines ... 

As pointed out above, fused silica used as a material for separation columns in capillary electrophoretic methods has normally a negative charge. Various ions, especially surfactants or big amphoteric ions, can be, however, adsorbed on the surface, which dramatically influences the zeta potential. For example, the addition of a small concentration of a suitable cationic surfactant like tetradecyltrimethylammonium bromide to the BGE causes its adsorption at the inner capillary wall and the reversal of the EOF in silica capillaries to the anodic side. Such surfactants are... 

A surfactant is a material that has fixed hydrophilic and lipophilic groups and can arrange directionally and absorb on the surface of a solution and reduce the surface tension of the solution significantly. Surfactants can be divided into anionic, cationic, nonionic, and amphoteric ions. The most common anionic surfactants are senior fatty acids and their salts, and the most common cationic surfactants are senior amines and their salt. The nonionic surfactants are silicone oil, fatty alcohol polyoxyethylene ether, fatty acid polyoxyethylene ether, and so forth. 

In FD, the sample is deposited directly onto carbon dendrites serving on the anode as activated emitters. For hydrocarbon-type anionic, cationic, and nonionic surfactants, FD usually produces molecular or quasimolecular ions free of fragmentation. For amphoteric nonfluorinated surfactants, molecular ions have been obtained together with fragment ions providing structural information [95-97], which showed that perfluoroalkanesulfonates are desorbed as high-mass clusters under FD conditions. 

From the ESI-FIA-MS(+) spectrum in Fig. 2.5.10(b), the amphoteric amine oxide surfactants ([M]+ ions at m/z 230, 258 and 286) and their dimeric ions ([2M - H]+ at m/z 459 and 487 (230 combined with 258)) could be recognised. The identity of the amine oxides was confirmed by recording product ions of the [M]+ ion at m/z 230 before the parent ion scan of fragment m/z 58 and vice versa was recorded for confirmation. This spectrum contained the A m/z 28 equally spaced characteristic amine oxide homologue ions at m/z 230, 258 and 286. 

This ESI(+) TIC, however, is dominated by strong and broad signals that eluted between 17 and 31 min, neither observable under APCI(+/—) nor ESI(-) conditions. Even under gradient RP-C18 conditions a strong tailing effect was observed while isocratic RP-C18 failed. The information obtained by ESI—LC—MS(+) was that the compounds could be ionised in the form of [M]+ ions at m/z 230, 258 and 286. ESI-LC-MS-MS(+) resulted in product ion spectra which, by means of a MS-MS library, were found to be characteristic for the amphoteric amine oxide surfactants. These compounds not yet observed in household formulations will be presented later on with the RIC of LC separation (cf. Fig. 2.5.11(d)). After identification as amine oxides, the separation and detection of this compound mixture now could be achieved by an isocratic elution using a PLRP-column and methane sulfonic acid and ESI(+) ionisation with the result of sharp signals (RT = 4-6 min) as presented in Fig. 2.5.11(d). 

Therefore, a C13-AE, a cationic (quaternary ammonium) surfactant (quat), an amphoteric Ci2-alkylamido betaine, and the non-ionic fatty acid diethanol amide (FADA) as presented with their FIA-MS spectra in Fig. 2.5.12(a)-(d) were analysed as pure blends and as mixtures always obtained from two blends in FIA-MS multiple ion detection mode (MID). Mixtures as well as pure blends contained identical concentrations of surfactant homologues. For AE quantitation the mass traces of all A m/z 44 equally spaced homologues (m/z 306-966) of the C13-AE were recorded. The cationic (quaternary ammonium) surfactant, the amphoteric Ci2-alkylamido betaine, and the non-ionic FADA were quantified recording the mass traces at m/z 214 and 228, or 184, 212, 240, 268, 285, 296, 313, 324 and 341, or 232,260, 288, 316 and 344, respectively. 

Levine, L.H. Garland, J.L. Johnson, J.V. HPLC/ESI-Quadrupole Ion Trap-MS for Characterization and Direct Quantification of Amphoteric and Nonionic Surfactants in Aqueous Samples. Anal. Chem. 2002, 74, 2064-2071. 

Surfactants are classified on the basis of the charge carried by the polar headgroup as anionic, cationic, nonionic, and amphoteric. Surfactant headgroups are dipoles, especially ionic ones that exist as ion pairs in hydrocarbon solvents. Electrostatic dipole-dipole attraction between headgroups in hydrocarbon solvents is the driving force for the formation of reverse micelles, or micellar aggregates, see Fig. 3.1 and Fig. 3.2. 

Hidaka H, Nohara K, Zhao J, Pelizzetti E, Serpone N. Photodegradation of surfactants. XIV. Formation of NH and NO, ions for the photocatalyzed mineralization of nitrogen-containing cationic, non-ionic and amphoteric surfactants. J Photochem Photobiol A Chem 1995 91 145-52. 

L.H. Levine, J.L. Garland, J.V. Johnson, LC-ESl-quadrupole ion trap MS for characterization and direct quantification of amphoteric and nonionic surfactants in aqueous samples. Anal. Chem., 74 (2002) 2064. 

Leon-Gonzalez et al.[31] proposed an FI spectrophotometric method for the determination of Triton-type non-ionic surfactants based on their reaction with alizarin fluorine blue. An on-line ion-exchange column was incorporated in the system to eliminate interferences from ionic and amphoteric surfactants. In case of interferences from non-ionic surfactants, an on-line Amberlite XAD-4 adsorption column was used to retain selectively the Triton-type surfactant, which was subsequently eluted by ethanol. However, no information was given regarding interferences from refractive index effects at the ethanol/aqueous interface and their elimination. 

The other part of the surfactant molecule, the polar end, is called the hydrophilic (water-loving) end. This end is normally an ionic end with a negative charge (anionic), a positive charge (cationic), or both (amphoteric). There are even some surfactants that have no charge (nonionic). (Ions, anions, cations — Chapter 6 explains em all.)... 

Dimethylaminopropylamine is an aliphatic amine present in amphoteric surfactants such as liquid soaps and shampoos. It is present as an impurity responsible for allergy from cocamidopropylbetaine. It is structurally similar to diethylaminopropylamine. It is also used as a curing agent for epoxy resins and as an organic intermediate in chemical syntheses (ion exchangers, additives for flocculants, cosmetics and fuel additives, dyes and pesticides). 

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