Effect of counter-anion concentration on retention in high-performance liquid chromatography of protonated basic analytes

LoBrutto, Rosario; Jones, A. D.; Kazakevich, Yuri

doi:10.1016/s0021-9673(00)01031-1

Cited by 89 publications

(46 citation statements)

References 31 publications

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“…The effect of TFA concentration-In principle, TFA can play three different roles in the cation-exchange separations studied here: (1) the proton from TFA, which at the concentrations employed here is almost fully dissociated, acts as the cationic displacer to exchange with cationic amines; (2) TFA in the mobile phase controls the pH and thus the charge status of the solutes; and (3) the trifluoroacetate resulting from the dissociation of TFA can act as an ion pairing agent in the mobile phase [5,6,38,39]. We believe that the third process has little effect on the retention of catecholamines because trifluoroacetate is not a sufficiently strong ion pairing agent to form ion pairs with the extremely hydrophilic catecholamines.…”

Section: 1the Separation Of Catecholaminesmentioning

confidence: 99%

Application of silica-based hyper-crosslinked sulfonate-modified reversed stationary phases for separating highly hydrophilic basic compounds

Luo

Paek

et al. 2008

Journal of Chromatography A

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The separation and determination of hydrophilic basic compounds are of great importance in many fields including clinical and biological research, pharmaceutical development and forensic analysis. However, the most widely used analytical separation technique in these disciplines, reversed-phase liquid chromatography (RPLC), usually does not provide sufficient retention for several of the important classes of highly hydrophilic basic compounds including catecholamines, many drug metabolites and many drugs of abuse. Commonly eluents having little or no organic modifier and/ or strong ion pairing agents must be used to achieve sufficient retention and separation. Use of highly aqueous eluents can lead to column failure by dewetting, resulting in poor retention, selectivity, reproducibility and slow recovery of performance. The use of a strong ion pairing agent to increase retention renders the separation incompatible with mass spectrometric detection and complicates preparative separations. This paper describes the successful applications of a novel type of silica-based, hyper-crosslinked, sulfonate-modified reversed stationary phase, denoted as − SO 3 -HC-C 8 -L, for the separation of highly hydrophilic cations and related compounds by a hydrophobically assisted cation-exchange mechanism. Compared to conventional reversed-phases, the − SO 3 -HC-C 8 -L phase showed significantly improved retention and separation selectivity. Concurrently, due to the presence of both cation-exchange and reversed-phase retention mechanisms and the high acid stability of hypercrosslinked phases, the separation can be optimized by changing the type or concentration of ionic additive or organic modifier, and by varying the column temperature. In addition, gradients generated by programming the concentration of either the ionic additive or the organic modifier can be applied to reduce the analysis time without compromising resolution. Furthermore, remarkably different chromatographic selectivities, especially toward cationic solutes, were observed upon comparison of the − SO 3 -HC-C 8 -L phase with conventional reversed-phases. We believe that the combination of these two types of stationary phases will be very useful in two-dimensional liquid chromatography.

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Section: 1the Separation Of Catecholaminesmentioning

confidence: 99%

Application of silica-based hyper-crosslinked sulfonate-modified reversed stationary phases for separating highly hydrophilic basic compounds

Luo

Paek

et al. 2008

Journal of Chromatography A

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“…We believe that two competitive processes are involved in altering the retention of amines: a reduction in the interaction with sulfonic groups, and an increase in retention by enhancing hydrophobic interaction. According to previous discussions [27,29,32], chaotropic anions such as ClO 4 − and CF 3 COO − , can create ion-associated complexes with protonated basic molecules [11,26]. Formed ion-pairs underwent longer retention as a more hydrophobic species [33].…”

Section: The Effect Of Anion Modifiersmentioning

confidence: 92%

Selective separation and purification of highly polar basic compounds using a silica-based strong cation exchange stationary phase

Zhang

Guo

Xue

et al. 2013

Analytica Chimica Acta

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“…Protonated basic analytes could interact with anions creating neutral ion-pairs with longer retention. In this case ion-associated complexes are formed only with that ones exhibiting chaotropic properties (H 2 PO 4 -<HCOO -<CH 3 SO 3 -<Cl -<NO 3 -<CF 3 COO -<BF 4 -<ClO 4 -<PF 6 -) (LoBrutto et al, 2001;Flieger, 2006). So far, adsorption of ILs on adsorbent surface and ion-pairing mechanism has been proposed to explain retention mechanism in chromatography applying ILs as modifiers.…”

Section: Ionic Liquids As Mobile Phase Modifiersmentioning

confidence: 99%

Application of Ionic Liquids in Liquid Chromatography

Flieger¹

2011

Ionic Liquids: Applications and Perspectives

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Effect of counter-anion concentration on retention in high-performance liquid chromatography of protonated basic analytes

Cited by 89 publications

References 31 publications

Application of silica-based hyper-crosslinked sulfonate-modified reversed stationary phases for separating highly hydrophilic basic compounds

Application of silica-based hyper-crosslinked sulfonate-modified reversed stationary phases for separating highly hydrophilic basic compounds

Selective separation and purification of highly polar basic compounds using a silica-based strong cation exchange stationary phase

Application of Ionic Liquids in Liquid Chromatography

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