Evaluation of a combined linear-nonlinear approach for column characterization using modern alkaline-stable columns as model

Undin, Torgny; Samuelsson, Jörgen; Törncrona, Anders; Fornstedt, Torgny

doi:10.1002/jssc.201201132

Cited by 20 publications

(8 citation statements)

References 32 publications

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“…The peak broadening of the basic compound is very serious in Prep-LC and very sensitive to the amount of sample loading. Although the loadability may be improved at alkaline pH, due to the solubility of basic compounds at high pH mobile phases and high-pH-stable columns etc., it cannot completely solve the problems of bases [24][25][26].…”

Section: The Design and Selection Of The Samples And Columnsmentioning

confidence: 99%

Practical method for the definition of chromatographic peak parameters in preparative liquid chromatography

et al. 2016

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A practical method was established for the definition of chromatographic parameters in preparative liquid chromatography. The parameters contained both the peak broadening level under different amounts of sample loading and the concentration distribution of the target compound in the elution. The parameters of the peak broadening level were defined and expressed as a matrix, which consisted of sample loading, the forward broadening and the backward broadening levels. The concentration distribution of the target compound was described by the heat map of the elution profile. The most suitable stationary phase should exhibit the narrower peak broadening and it was best to broaden to both sides to compare to the peak under analytical conditions. Besides, the concentration distribution of the target compounds should be focused on the middle of the elution. The guiding principles were validated by purification of amitriptyline from the mixture of desipramine and amitriptyline. On the selected column, when the content of the impurity desipramine was lower than 0.1%, the recovery of target compound was much higher than the other columns even when the sample loading was as high as 8.03 mg/cm . The parameters and methods could be used for the evaluation and selection of stationary phases in preparative chromatography.

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Section: The Design and Selection Of The Samples And Columnsmentioning

confidence: 99%

Practical method for the definition of chromatographic peak parameters in preparative liquid chromatography

et al. 2016

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“…The reason why the peak shapes of the neutral compounds is more symmetrical than those of ionizable compounds is that their binding constant on these “active” sites is much smaller than that experienced by the ionizable compounds for comparable retention factors. Indeed, the elution of ions requires always a larger amount of water in the eluent than that necessary to elute neutral chemicals .…”

Section: Resultsmentioning

confidence: 99%

Hydrophilic interaction chromatography: A promising alternative to reversed‐phase liquid chromatography systems for the purification of small protonated bases

Gritti

Guiochon

2015

J of Separation Science

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The overloaded band profiles of the protonated species of propranolol and amitriptyline were recorded under acidic conditions on four classes of stationary phases including a conventional silica/organic hybrid material in reversed-phase liquid chromatography mode (BEH-C18), an electrostatic repulsion reversed-phase liquid chromatography C18 column (BEH-C18+), a poly(styrene-divinylbenzene) monolithic column, and a hydrophilic interaction chromatography stationary phase (underivatized BEH). The same amounts of protonated bases per unit volume of stationary phase were injected in each column (16, 47, and 141 μg/cm(3)). The performance of the propranolol/amitriptyline purification was assessed on the basis of the asymmetry of the recorded band profiles and on the selectivity factor achieved. The results show that the separation performed under reversed-phase liquid chromatography like conditions (with BEH-C18, BEH-C18+, and polymer monolith materials) provide the largest selectivity factors due to the difference in the hydrophobic character of the two compounds. However, they also provide the most distorted overloaded band profiles due to a too small loading capacity. Remarkably, symmetric band profiles were observed with the hydrophilic interaction chromatography column. The larger loading capacity of the hydrophilic interaction chromatography column is due to the accumulation of the protonated bases into the diffuse water layer formed at the surface of the polar adsorbent. This work encourages purifying ionizable compounds on hydrophilic interaction chromatography columns rather than on reversed-phase liquid chromatography columns.

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“…The C 18 phases are heterogeneous , and thus not purely hydrophobic; therefore, there are interactions also between charged protolytic compounds and the C 18 stationary phases. Before the introduction of hybrid phases , basic compounds were separated at pH 2–3 where the basic compounds are eluting in their charged salt form as ion‐pair complexes with inorganic buffer ions. However, these complexes are not adsorbed as strongly on the C 18 phases as the uncharged forms of the basic or acidic compounds.…”

Section: Methodsmentioning

confidence: 99%

“…In this context, it is worth mentioning that in RP‐LC using C 18 phases not only hydrophobic interactions take place but also polar and ionic interactions are responsible for the mechanism . Therefore, organic bases with p K a values around 9 are normally eluted at low pH when the bases are charged, if not hybrid columns are used to allow separation at extreme pH levels .…”

Section: Introductionmentioning

confidence: 99%

Sample conditions to avoid pH distortion in RP‐LC

Samuelsson

Forssén

Fornstedt

2013

J of Separation Science

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Band deformations might take place for acids and bases in preparative applications and adsorption studies where it is necessary to use overloaded injections. In this study, we focus on how deformations can be prevented without using highly concentrated buffers that may precipitate in the eluent. We have systematically investigated how the elution zones depend on which protolytic form the analyte has when it is dissolved. Basic and acidic model compounds are investigated using eluents with different pH values and the resulting elution profiles are compared when the analytes are dissolved in their protonated and deprotonated form, i.e., in uncharged form or as different kinds of salts. Depending on the analyte's protolytic form, a sample zone is created at the column inlet whose pH deviates, more or less, from the bulk eluent's. If the local adsorption strength in this sample zone is greater than the bulk eluent's, the elution profiles are compressed. Under opposite conditions, the eluted bands are more or less deformed and may even be split; completely different deformations can even take place for different kinds of salt combinations. Explanations of these, and other, effects, together with detailed guidelines for proper sample preparation to avoid peak deformations, are given.

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Evaluation of a combined linear-nonlinear approach for column characterization using modern alkaline-stable columns as model

Cited by 20 publications

References 32 publications

Practical method for the definition of chromatographic peak parameters in preparative liquid chromatography

Practical method for the definition of chromatographic peak parameters in preparative liquid chromatography

Hydrophilic interaction chromatography: A promising alternative to reversed‐phase liquid chromatography systems for the purification of small protonated bases

Sample conditions to avoid pH distortion in RP‐LC

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