Cationic surfactants chromatography

Harrison, C.R., Lucy, C.A. (2002). Determination of zwitterionic and cationic surfactants by high-performance liquid chromatography with chemiluminescent nitrogen detection. J. Chromatogr. A 956(1-2), 237-244. 

Numerous applications have been shown to exist that overcome the general problems of lack of volatility and instability at higher temperatures that principally hamper direct analysis of surfactants by GC methods. Thus, a whole suite of derivatisation techniques are available for the gas chromatographist to successfully determine anionic, non-ionic and cationic surfactants in the environment. This enables the analyst to combine the high-resolution chromatography that capillary GC offers with sophisticated detection methods such as mass spectrometry. In particular, for the further elucidation of the complex mixtures, which is typical for the composition of many of the commercial surfactant formulations, the high resolving power of GC will be necessary. 

Ion-exchange chromatography techniques that provide cationic surfactant residues suitable for a conductivity analysis are also developed [47,48]. They usually employ strong cation exchange columns and a mobile-phase based on an organic solvent (acetonitrile or... 

Several techniques have been developed for the trace analysis of cationic surfactants. Most of the methodologies are based on high-performance liquid chromatography (HPLC) techniques, because most of the commercial cationic surfactants are produced as homologous... 

C.-E. Lin, Y.-T. Chen and T.-Z. Wang, Separation of benzenediamines, benzenediols and aminophenols in oxidative hair dyes by micellar electrokinetic chromatography using cationic surfactants. J. Chromatogr.A, 837 (1999) 241-252. 

Norberg, J., E. Thordarson, L. Mathiasson, and J.A. Jonsson. 2000. Microporous membrane liquid-liquid extraction coupled on-line with normal-phase liquid chromatography for the determination of cationic surfactants in river and waste water. J. Chromatogr. A 869 523-529. 

Crosby D, El Rassi Z. Micellar electrokinetic capillary chromatography with cationic surfactants. J Liq Chromatogr 1993 16 2161. 

Sainthorant C, Morin P, Dreux M, Baudry A, Goetz N. Separation of phenylenedia-mine, phenol and aminophenol derivatives by micellar electrokinetic chromatography. comparison of the role of anionic and cationic surfactants. J Chromatogr A 1995 717 167. 

Micelles and cyclodextrins are the most common reagents used for this technique. Micellar electrokinetic capillary chromatography (MECC or MEKC) is generally used for the separation of small molecules [6], Sodium dodecyl sulfate at concentrations from 20 to 150 mM in conjunction with 20 mM borate buffer (pH 9.3) or phosphate buffer (pH 7.0) represent the most common operating conditions. The mechanism of separation is related to reversed-phase liquid chromatography, at least for neutral solutes. Organic solvents such as 5-20% methanol or acetonitrile are useful to modify selectivity when there is too much retention in the system. Alternative surfactants such as bile salts (sodium cholate), cationic surfactants (cetyltrimethy-lammonium bromide), nonionic surfactants (poly-oxyethylene-23-lauryl ether), and alkyl glucosides can be used as well. 

In a study of ion-pair chromatography with cationic surfactants, which - according to the... 

As in cationic surfactants, very few liquid chromatographic methods are described in the literature for characterizing sulfonium salts. In a recent paper, Anklam et al. [45] showed that five- and six-membered cyclic sulfonium salts of the following structure are easily analyzed via ion-pair chromatography. 

Surfactants that can presently be analyzed by means of ion chromatography are summarized in Table 8-5. Up until now, surfactants were analyzed by a two-phase titration [45,46]. This technique is based on an equilibrium reaction between surfactant dyes and anionic/cationic surfactant salts and their distribution between chloroform and water in a two-phase mixture. Hyamine 1622 (bis-j -butyl-phenoxyethyl-dimethyl-benzylam-... 

IR spectroscopy is used for the qualitative identihcation of surfactants and for differentiating between them and nonsurfactant compounds. Prior to IR spectroscopy, however, separation of the organic compound complex into different fractions, performed by, e.g., the use of thin-layer chromatography, is required to obtain meaningful spectra. °" ° By comparing the IR spectra of the isolated fractions with IR spectra of standard compounds with regard to characteristic bands, the qualitative determination of surfactants in environmental samples is possible. The method is equally applicable to anionic, ° nonionic, °" and cationic surfactants.The prerequisite for a clear identification of surfactants, however, is the availability of suitable standards. Moreover, considerable experience and knowledge are needed to interpret IR spectra of environmental samples. 

Morin, Ph., Villard, F., Quinsac, A., and Dreux, M. MiceUar electrokinetic capUlary chromatography of glu-cosinolates and desulfoglucosinolates with a cationic surfactant, J. High Resolut. Chromatogr., 371, 1992. 

C.-E. Lin, C.-C. Hsueh, T.-Z. Wang, T.-C. Chiu and Y.-C. Chen, Migration behavior and separation of s-triazines in micellar electrokinetic capillary chromatography using a cationic surfactant,... 

E. Blanco, M.C. Casais, M.C. Mejuto and R. Cela, Approaches for the simultaneous extraction of tetrabromobisphenol A, tetrachlorobisphenol A and related phenolic compounds from sewage sludge and sediment samples based on matrix sohd-phase dispersion, J. Chromatogr. A, 78, 2772-2778, 2006. S. Takeda, A. Omura, K. Chayama, H. Tsuji, K. Fukushi, M. Yamane, S.-I. Wakida, S. Tsubota and S. Terabe, Separation and on-line concentration of bisphenol A and alkylphenols by micellar electrokinetic chromatography with cationic surfactant, J. Chromatogr. A, 979, 425-429, 2002. 

The same relates to the analytical methods, where for anionic, nonionic and cationic surfactants, various colorimetric procedures (MBAS, bismuth active substance(s) (BiAS), and disulfine blue active substance(s) (DSBAS)) were introduced. Since these methods analyse only the loss of surface-activity or primary degradation, other analytical approaches have been employed in the last 10 years in order to characterize the total or ultimate degradation. These include methods such as high performance liquid chromatography (HPLC), gas chromatography (GC) GC/mass spectrometry (MS), and the measurement of total organic carbon (TOC) and chemical oxygen demand (COD). 

It is always recommended to use the same column with the same type of surfactant. A column should be dedicated to the anionic surfactants, a second one to the cationic surfactants, etc. The reproducibility of the results in MLC depends on the column equilibration. The adsorbed layer of surfactant should be done correctly. It was shown that the time to reach the equilibrium between the stationary phase and the mobile phase could be very long in ion-pair chromatography with sub-micellar mobile phases. Two days at 1 mL/min were necessary to equilibrate a 15 cm x 4.6 mm i.d. column of Hypersil ODS with a mobile phase containing 0.0003 M CTAB [19]. These low surfactant concentration solutions do not contain micelles. So, they are not used in MLC. With a micellar phase, the equilibration time is reduced. It is possible to use the rapid gradient capability just mentioned above. Typically, a mobile phase containing a high surfactant concentration (10 to 100 cmc) can be used to quickly saturate the column with surfactant. Then 5 to 10 column volumes are used to rinse the column with the mobile phase containing the desired amount of surfactant. 

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