Effect of the organic modifier concentration on the retention in reversed-phase liquid chromatography

1,076

818

Separation of polar compounds on polar stationary phases with partly aqueous eluents is by no means a new separation mode in LC. The first HPLC applications were published more than 30 years ago, and were for a long time mostly confined to carbohydrate analysis. In the early 1990s new phases started to emerge, and the practice was given a name, hydrophilic interaction chromatography (HILIC). Although the use of this separation mode has been relatively limited, we have seen a sudden increase in popularity over the last few years, promoted by the need to analyze polar compounds in increasingly complex mixtures. Another reason for the increase in popularity is the widespread use of MS coupled to LC. The partly aqueous eluents high in ACN with a limited need of adding salt is almost ideal for ESI. The applications now encompass most categories of polar compounds, charged as well as uncharged, although HILIC is particularly well suited for solutes lacking charge where coulombic interactions cannot be used to mediate retention. The review attempts to summarize the ongoing discussion on the separation mechanism and gives an overview of the stationary phases used and the applications addressed with this separation mode in LC.

Section: Mechanismmentioning

confidence: 99%

Hydrophilic interaction chromatography

Hemström

Irgum²

2006

1,076

818

“…The purpose of this study is a comparison of the performance of four (presented above) very valuable retention models assuming the partition and adsorption mechanism of retention, by fitting them to experimental k = f(u) data. These models give very good fitting results in different systems with classical C 8 and C 18 columns [5,9,19,21]. Therefore it seems interesting to know how these equations fit the retention data obtained for C 30 column for which, as can be seen below, strongly non-linear k = f (u) dependences were observed.…”

Section: Introductionmentioning

confidence: 83%

“…This equation was developed within the framework of the adsorption model based on a semi-thermodynamic approach and takes into account the interaction of the solute with the modifier and solvent only in the adsorbed layer [19]. The employment of chemically bonded stationary phases composed of partially non-bonded silica matrix and organic ligands bonded to its surface in everyday chromatography practice leads to the question of the correct definition of the retention model and the dominant retention mechanism in such chromatographic systems.…”

Section: Introductionmentioning

confidence: 99%

Brief analysis of the retention process in RP‐HPLC systems with a C₃₀ bonded stationary phase

Zapała¹

2008

The influence of the mobile-phase composition on the retention of eight model substances in different RP-HPLC systems with a C(30) alkyl bonded stationary phase has been studied. The aim of this study was to compare the performance of four valuable retention models assuming the partition and adsorption mechanism of retention. All the models were verified for different experimental data by four criteria: the sum of squared differences between the experimental and theoretical data; the approximation of the standard deviation; the Fisher test; and the F-test ratio.

“…. ., n; usually n is not greater than 2) in the mobile phase and their corresponding concentrations (C i ) [23,24]. This influence on retention (represented as the ten-base logarithm of the capacity factor, k) is described via a second order (j = 2) polynomial equation, according to relationship:…”

Section: Influence Of the Organic Component Of The Mobile Phase On Rementioning

confidence: 99%

Competitional hydrophobicity driven separations under RP‐LC mechanism: Application to sulfonylurea congeners

David¹,

Galaon²,

Caiali

et al. 2009

Retention of a model set of sulfonylurea compounds has been studied under RP-LC conditions, considering competitional effects brought by different alcohols (ethanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol, and 1-octanol) used as additives in the organic component of the mobile phase (methanol). The capacity factors determined for the model compounds decreased with the increase of the hydrophobic character of the organic additive in the mobile phase. The amount of the additive within the organic component of the mobile phase was kept constant (1% as volumetric ratio). Retention was studied at different mobile phase compositions (aqueous to organic component ratios). Different functional fitting models were used to correlate retention to the content of the organic component in the mobile phase. Extrapolation of retention expressed as capacity factor to a mobile phase composition free of organic component is well correlated to the hydrophobic characteristics of the organic additives. The adsorption model was used for tuning the experimental find-outs. The possibility of controlling retention through the competitive effects induced by hydrophobic additives in the mobile phase is highlighted.