Evaluation of the use of microemulsions as eluents in high‐performance liquid chromatography

El-Sherbiny, Dina T.; El‐Ashry, Saadia M.; Mustafa, Mohamed Ahmed; El-Emam, Ali A.; Hansen, Steen Honoré

doi:10.1002/jssc.200390067

Cited by 42 publications

(27 citation statements)

References 17 publications

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“…Water-soluble analytes will reside mainly in the aqueous phase and their retention is largely controlled by stationary phase interactions. The hydrophobic organic solvents used to create the droplets are also distributed to some extent on the surface of the column, which increases the amount of stationary phase and also affects solute selectivity and retention [8]. Together, all of these partitioning mechanisms control the retention and separation of solutes in an MELC separation.…”

Section: Background To O/w and W/o Melcmentioning

confidence: 99%

A review of the background, operating parameters and applications of microemulsion liquid chromatography (MELC)

Marsh

Clark

Altria³

2005

J of Separation Science

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A review of the background, operating parameters and applications of microemulsion liquid chromatography (MELC) Microemulsions are dispersions of nanometre-sized droplets of an immiscible liquid within another liquid. Droplet formation is facilitated by the addition of surfactants and often also cosurfactants. Microemulsions are classified as either oil-in-water (O/W) (oil droplets such as octane dispersed throughout aqueous buffer) or water-in-oil (W/O) (aqueous droplets in oil such as hexane). Both microemulsion types have been used as mobile phases for separation in microemulsion HPLC (MELC). There has been a recent increase of interest in this area with new applications and developments such as gradient elution and optimisation of methods using experimental design. O/W microemulsions have been employed as eluents for RP-HPLC while W/O microemulsions have been used for normal phase chromatography. Separations can have superior speed and efficiency to conventional HPLC modes while offering a unique selectivity with excellent resolution. The capability for quantitative and stability-indicating analysis has also been demonstrated. Specific advantages include the ability to operate at low UV wavelengths and elimination of the need for an equilibration rinse between gradients. Operational issues associated with the use of MELC have been identified including the need to add salt to the gradient eluent, relatively high back-pressures and increased need for equipment cleaning compared to conventional RP eluent. This report details the different microemulsion types and compositions used and their reported applications. The use of gradient and isocratic elution is described. The effects on separations of varying operating parameters such as temperature, oil type and concentration, surfactant type and concentration, sample solvent, column type, and organic solvent addition will be discussed and illustrated.

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Section: Background To O/w and W/o Melcmentioning

confidence: 99%

A review of the background, operating parameters and applications of microemulsion liquid chromatography (MELC)

Marsh

Clark

Altria³

2005

J of Separation Science

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“…However, hydrophobic organic solvents that represent the internal phase of microemulsion eluent, as well as the molecules of surfactant, may bind to the stationary phase and therefore induce the significant changes of its characteristics. 1 That is why the prediction of retention behavior may be more complicated.…”

Section: Microemulsions As Eluents In Liquid Chromatographymentioning

confidence: 99%

Physicochemical factors governing the partition of pramipexole and its five impurities in microemulsion liquid chromatographic systems

Vemić¹,

Malenović²,

Rakić³

et al. 2012

J. Braz. Chem. Soc.

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As microemulsões, quando usadas como fase móvel, representam uma ferramenta cromatográfica poderosa devido à sua estrutura polifásica. O objetivo deste estudo foi investigar a influência da composição da fase móvel e as propriedades das gotículas resultantes da microemulsão, bem como a lipofilicidade da fase estacionária no comportamento cromatográfico de pramipexol e suas cinco impurezas. A investigação foi realizada de acordo com o plano experimental definido pelo planejamento fatorial completo 2 4 com quatro repetições do ponto central. Embora o mais afetado pelas características da coluna tenha sido o último eluente, a substância mais lipofílica, a composição e as características das gotículas de microemulsão foram igualmente importantes, de modo que o sistema de partição gotículas de microemulsão/fase estacionária provou ser o mais significativo. A lipofilicidade da fase estacionária não afetou o componente mais hidrofílico e somente o sistema de partição gotículas de microemulsão/volume do eluente causou impacto em seu comportamento. Para a separação do par crítico, foram notados efeitos quase iguais dos sistemas de partição gotículas de microemulsão/fase estacionária e volume do eluente/fase estacionária.Microemulsions when used as mobile phases represent a very powerful chromatographic tool due to their polyphase structure. The aim of this study was to investigate the influence of the mobile phase composition and resulting microemulsion droplet's properties, as well as the stationary phase lipophilicity on the chromatographic behavior of pramipexole and its five impurities. Investigation was carried out according to the experimental plan defined by a full factorial design 2 4 with four central point replications. While the most affected by column characteristics was the last eluting, most lipophilic substance, the composition and characteristics of microemulsion droplets were equally important, so the partition system microemulsion droplets/stationary phase proved to be the most significant. Stationary phase lipophilicity did not affect the most hydrophilic component and only the partition system microemulsion droplets/bulk of the eluent impacted its behavior. For the separation of the critical pair, almost equal effects of the microemulsion droplets/stationary phase and bulk of the eluent/stationary phase partition systems were noted.

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“…For example, in 1986, Dorsey and coworkers [11] first reported the feasibility of using w/o microemulsions as mobile phases in normal-phase HPLC, in which water molecules were trapped into reversed micelles and thus the deleterious effect of water molecules on the silica stationary phases was greatly reduced, but efficiency of separation was found to be very poor in general. More recently, Hansen and coworkers [12] demonstrated that comparable separation efficiencies to conventional HPLC can be achieved when using o/w microemulsions as mobile phases in RP HPLC. Advantages included much shorter retention times obtainable for lipophilic substances (thus avoiding the need of gradient elution), simpler sample preparation of lipophilic samples due to enhanced solubilization capacity of microemulsion solvents, as well as possible direct sample injection of biofluids.…”

Section: Introductionmentioning

confidence: 99%

Recent applications of microemulsion electrokinetic chromatography

Huie

2006

Electrophoresis

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Compared to MEKC, the presence of a water-immiscible oil phase in the microemulsion droplets of microemulsion EKC (MEEKC) gives rise to some special properties, such as enhanced solubilization capacity and enlarged migration window, which could allow for the improved separation of various hydrophobic and hydrophilic compounds, with reduced sample pretreatment steps, unique selectivities and/or higher efficiencies. Typically, stable and optically clear oil-in-water microemulsions containing a surfactant (SDS), oil (octane or heptane), and cosurfactant (1-butanol) in phosphate buffer are employed as separation media in conventional MEEKC. However, in recent years, the applicability of reverse MEEKC (water-in-oil microemulsions) has also been demonstrated, such as for the enhanced separation of highly hydrophobic substances. Also, during the past few years, the development and application of MEEKC for the separation of chiral molecules has been expanded, based on the use of enantioselective microemulsions that contained a chiral surfactant or chiral alcohol. On the other hand, the application of MEEKC for the characterization of the lipophilicity of chemical substances remains an active and important area of research, such as the use of multiplex MEEKC for the high-throughput determination of partition coefficients (log P values) of pharmaceutical compounds. In this review, recent applications of MEEKC (covering the period from 2003 to 2005) are reported. Emphases are placed on the discussion of MEEKC in the separation of chiral molecules and highly hydrophobic substances, as well as in the determination of partition coefficients, followed by a survey of recent applications of MEEKC in the analysis of pharmaceuticals, cosmetics and health-care products, biological and environmental compounds, plant materials, and foods.

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Evaluation of the use of microemulsions as eluents in high‐performance liquid chromatography

Cited by 42 publications

References 17 publications

A review of the background, operating parameters and applications of microemulsion liquid chromatography (MELC)

A review of the background, operating parameters and applications of microemulsion liquid chromatography (MELC)

Physicochemical factors governing the partition of pramipexole and its five impurities in microemulsion liquid chromatographic systems

Recent applications of microemulsion electrokinetic chromatography

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