Adsorption isotherm of tetrabutylammonium ion and its relation to the mechanism of ion pair chromatography

Abstract

To understand the mechanism of Ion pair chromatography, a correct description of the adsorption isotherm of the amphiphilic modifier Is Important. The adsorption Isotherm of tetrabutylammonlum Ion onto a RP-18 stationary phase Is determined with different electrolytic counterions (H2P04', CL, Br") and for two different Ionic strengths. The electrostatic surface potential created by the adsorbed tetrabutylammonlum Ions Is determined by applying the concepts of the electrostatic theory for Ion pair chromatography. The different experimentally determined adsorption Isotherms are found to coincide with the same surface-potential-modified Langmuir isotherm. The results are therefore In accordance with the electrostatic theory for Ion pair chromatography. ACKNOWLEDGMENTWe are most grateful to M. Almgren and B. Jonsson for valuable discussions during the preparation of this work and to A. Furángen for valuable discussions of the manuscript. The computer program for a numerical solution of the Poisson-Boltzmann equation was obtained from the

Method Development for the Acquisition of Adsorption Isotherm of Ion Pair Reagents Tributylamine and Triethylamine in Ion Pair Chromatography

“…It shows that the amount of TEtAA eluting from the column became lower than the LOQ at 6 CV, and LOD was reached already at 10 CV, which made us decide to use 10 CV (25mL) to determine the different points in the adsorption isotherm of TEtAA. Ståhlberg [22] used more than 80 CV to strip off the adsorbed tetrabutylammonium ions from C18 LiChrosorb column, using 80% acetonitrile-water as the stripping solvent while Hung and Taylor [21] used more than 200 CV to fulfil the same function, from ODS Hypersil column using neat ethanol as a stripping solvent. Although the solutes used by Ståhlberg [21] and Hung and Taylor [22] , were more hydrophobic than the ones used in this study, the quantity of eluent required for stripping was very large.…”

“…In this case, no identifiable monolayer is formed, the adsorbed solutes rather being clustered on the surface. The adsorption isotherms for tetraalkylammonium ions on reversed phase columns have been reported extensively under diverse chromatographic conditions [21][22][23][24][25] and these are type I isotherms. However, there is a paucity of information about the adsorption isotherms of trialkylammonium ions, and to the best of our knowledge, there are no published data in the scientific literature.…”

Perspective on the Future Approaches to Predict Retention in Liquid Chromatography

“…when different types of intermolecular interactions (e.g., dispersive and ionic interactions ,,, ) are relevant in the separation system. For instance, in order to account for hydrophobic interactions assisted by ionic interactions in RP/IEX mixed-mode chromatography (MMC), Stählberg and Hägglund proposed that a model from the electrostatic theory of ion-pair chromatography is physically suitable for the prediction of the retention factor k RP/IEX in MCC when the surface potential remains smaller than 40 mV. This retention model is given in the Supporting Information text. Stählberg’s model can be extended to cases where both the IEX ligand and the analyte are not permanently charged depending on the applied pH.…”

A Closer Study of Overloaded Elution Bands and Their Perturbation Peaks in Ion-Pair Chromatography

“…In ion-pair chromatography (IPC), a lipophilic component called the ion-pair reagent (IPR) is added to the mobile phase for the separation of polar or charged solutes such as inorganic and organic ions, proteins, peptides, oligonucleotides, and basic drugs in reserved-phase liquid chromatography systems [1][2][3][4] . Interest in IPC has been increasing greatly in recent years, as efficient separations of oligonucleotide and peptide pharmaceuticals require IPR in the mobile phase [5][6][7] .…”