Reversed phase ion-pair chromatography

Separation of ionic and nonionic compounds of alkyl ether carboxylates can be done by reverse phase ion pair chromatography [241]. 

Simple mixtures—like in alkyl sulfosuccinates—can be run using only one solvent. For more complex systems (e.g., ethoxylated fatty alcohol sulfosuccinates) a gradient technique is strongly recommended Technical mixtures of disodium laureth sulfosuccinate could be separated [68]. The separation was so effective that resolution of single homologs of ethoxylates was possible. The detection limit of this method lies at around 0.5 pg. Therefore reverse phase ion pair chromatography seems to be an excellent tool to analyze sulfosuccinates directly without the use of any kind of manipulation. 

Hapten density, and also the common positions where haptens are bound, can also be estimated by cyanogen bromide or enzymatic cleavage of the protein and either MALDI-MS or separation of the components by reversed-phase ion-pair chromatography and electrospray or electrospray time-of-flight (TOF) analysis. 

Steinbrech, B., Neugebauer, D., Zulauf, G. (1986). Determination of surfactants by liquid chromatography (HPLC). Reversed phase ion-pair chromatography of alkyl sulfates and alkyl sulfosuccinates. Analytische Chemie 324(2), 154—157. 

The recent use of HPLC for the analysis of sulfophenyl carboxylates (SPCs) has been one of the most interesting applications of this technique for the study of the environmental behaviour of anionic surfactants. SPCs are separated by reversed-phase ion-paired chromatography, in which a hydrophobic stationary phase is used and the mobile phase is eluted with aqueous buffers containing a low concentration of the counter-ion [19]. 

SCN Water Filtration (0.45 pm) Reversed-phase ion-pair chromatography with amperometric detection 104 ng/ml No data Xu etal. 1993... 

Xu J, Xin M, Takeuchi T, et al. 1993. Determination of oxidizable inorganic anions by reversed-phase ion-pair chromatography with amperometric detection. Anal Chim Acta 276(2) 261-264. 

A. Bartha, H.A.H. Billiet, L.D. Galan, and G. Vigh, Studies in reversed-phase ion-pair chromatography III. The effect of counter-ion concentration , J. Chromatogr., 1984, 291,91. 

A. Bartha, G. Vigh, H. Billiet, and L. de Galan, Effect of the type of ion-pairing reagent in reversed-phase ion-pair chromatography , Chromatographia, 1985,10, 587. 

For kilohertz measnrement frequencies and above, the contribution of Qi can generally be neglected. McWhorter and Soper employed a simple two-electrode contact conductivity detector with reverse-phase ion pair chromatography, and achieved a detection limit of 3.46pg in a lOOnL volume (464nM) for KCl [54]. Four-electrode setups, in which two leads are nsed to measure current and the other pair to measure voltage, can also be nsed in order to eliminate the effect of the impedance of the electrical leads on the measnrement. 

Reversed-phase ion-pair chromatography is primarily used for the separation of mixtures of ionic and ionizable compounds. In this chromatographic mode, a pairing ion is added to the mobile phase in order to modulate the retention of the ionic solutes. The pairing ion is an organic ion such as alkylsulfonate, alkylsulfate, alkylamine, tetraalkylammonium ion, etc. Here, only a very brief description of the main ideas behind the electrostatic model for ion-pair chromatography is presented. For a complete discussion, the reader is referred to Ref. [7,8] and the references therein. 

T Hayashi, H Tsuchiya, H Naruse. Reversed-phase ion-pair chromatography of amino acids. Application to the determination of amino acids in plasma samples and dried blood on filter papers. J Chromatogr Biomed Appl 274 318-324, 1983. 

Reversed-phase ion-pair chromatography was employed to quantify the chlorophylls and carotenoids in olive oil (36) using the following eluents (A) methanol/water/ion-pair reagent (0.05 M tetrabutylammonium and 1 M ammonium acetate), (B) acetone/methanol (1 1). 

Fairman, B., Catterick, T., Wheals, B. and Polinina, E. (1997) Reversed-phase ion-pair chromatography with inductively coupled plasma-mass spectrometry detection for the determination of organo-tin compounds in waters./. Chromatogr. A, 758, 85-92. 

M. L. Bieganowska, A. Petruczynik, and A. Doraczynska-Szopa, Thin-layer reversed-phase ion-pair chromatography of some sulphonamides, J. Pharm. Biomed. Anal., 77 241 (1993). 

For reversed-phase ion-pair chromatography a non-polar surface (e.g. Cg or C- g) is used as a stationary phase and an ionic alkyl compound is added to the aqueous mobile phase as a modifier. For the separation of acids, an organic base (e.g. tetrabutylammonium phosphate) is added to the eluent for the separation of bases, an organic acid (e.g. octane sulphonate) is used. Reversed-phase ion pairing is presently the most popular approach because of the simpler technical requirements and very high column performance. It is however essential to operate the system only after equilibrium of the mobile phase and the stationary phase has occurred in order to obtain reproducible analyses. 

The application of reversed-phase ion-pair chromatography to the separation of charged solutes has gained wide acceptance mainly because of the limitations of ion-exchange chromatography in... 

Gloor, R. and Johnson, E.L. Practical aspects of reversed phase ion-pair chromatography. J. Chromatogr. Sci. 1977, 15, 413 23. 

Stahlberg, J. and Bartha, A. Extension of the electrostatic theory of reversed-phase ion-pair chromatography for high surface concentrations of the adsorbing amphiphilic ion. 

Li, J. Prediction of internal standards in reversed-phase liquid chromatography IV correlation and prediction of retention in reversed-phase ion-pair chromatography based on linear solvation energy relationships. Anal. Chim. Acta 2004, 522, 113-126. 

Pang, X.Y., Sun, H.W., and Wang, Y.H. Determination of sulfides in synthesis and isomerization systems by reversed-phase ion-pair chromatography with a mobile phase containing tetramethylene oxide as organic modifier. Chromatographia 2003, 57, 543-547. 

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