Enhancement of retention by ion-pair formation in liquid chromatography with nonpolar stationary phases

Horváth, Csaba; Melander, Wayne R.; Molnár, Imre; Molnár, Petra Magdolna

doi:10.1021/ac50022a048

Cited by 411 publications

(128 citation statements)

References 23 publications

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“…Even though this problem can be avoided by choosing from the relative limited variety of special reversedphases designed for use in very water rich media [13], an additional and we believe much more serious problem is that use of such a small fraction of organic modifier leaves only a very narrow range in eluent conditions for optimizing the separation via manipulating the eluent composition. Strong ion pairing agents, such as surfactants with long alkyl chains, are also commonly used [7][8][9]14,15] to increase retention through either ion pairing in the mobile phase [14], or dynamic ion exchange in the stationary phase [5,16,17]. However, the addition of strong ion pairing reagents to the eluent is not desirable because (1) it makes the separation incompatible with mass spectrometric detection, (2) it is hard to recover the column after use since these additives tend to stick very strongly to the stationary phase, and (3) it is not practical in preparative separations.…”

Section: Introductionmentioning

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: Introductionmentioning

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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“…Below the pI of a 59 protein or peptide, basic amino acid residues (lysine, arginine, histidine, and also the N-60 terminus) will become protonated, which may form ion pairs with anions present in the 61 mobile phase. Ion pairing increases hydrophobicity of the protein, which changes the 62 interaction with the reversed phase [20,21]. Trifluoroacetic acid (TFA) is a widely used ion 63 pairing additive, but its effect on protein structure and the retention mechanism is not clearly 64 understood.…”

mentioning

confidence: 99%

Influence of acid-induced conformational variability on protein separation in reversed phase high performance liquid chromatography

Bobály

Tóth

Drahos

et al. 2014

Journal of Chromatography A

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“…While it is best suited for non-polar analytes, retention of polar analytes such as amino acids is possible by adding an ion pairing reagent (IPR) to the mobile phase. The IPR forms an ion pair with the polar analyte reducing its polarity and enhancing its interaction with the non-polar stationary phase [79] Trifluoro acetic acid (TFA) [80,81], sodium perchlorate [81] and pentadecafluorooctanoic acid [82] are some examples of IPR.…”

Section: Quantification Of the Compatible Osmolytes Proline Betaine mentioning

confidence: 99%

A Review of Extraction and Analysis: Methods for Studying Osmoregulants in Plants

Kalsoom¹,

Bennett²,

Boyce³

2016

J Chromatogr Sep Tech

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Enhancement of retention by ion-pair formation in liquid chromatography with nonpolar stationary phases

Cited by 411 publications

References 23 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

Influence of acid-induced conformational variability on protein separation in reversed phase high performance liquid chromatography

A Review of Extraction and Analysis: Methods for Studying Osmoregulants in Plants

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