Optimisation and use of water-in-oil MEEKC in pharmaceutical analysis

Broderick, Margo; Donegan, Sheila; Power, Joe; Altria, Kevin D.

doi:10.1016/j.jpba.2004.07.047

Cited by 24 publications

(27 citation statements)

References 20 publications

(26 reference statements)

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“…Typically, oil-in-water microemulsions (o/w) are utilized for both achiral and chiral MEEKC work [42]. Fewer articles detailing water-in-oil microemulsions (w/o) have been published, and none have reported the separation of enantiomers [47,48]. The structure of o/w nanodroplets consists of an oil core (alkane or water immiscible substance) surrounded by a surfactant/cosurfactant layer; the cosurfactant is a short chain alcohol and is interdispersed among the surfactant molecules.…”

Section: Introductionmentioning

confidence: 99%

Two‐chiral component microemulsion EKC – chiral surfactant and chiral oil. Part 2: Diethyl tartrate

Kahle

Foley

2007

Electrophoresis

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In this second study on dual-chirality microemulsions containing a chiral surfactant and a chiral oil, a less hydrophobic and lower interfacial tension chiral oil, diethyl tartrate, is employed (Part 1, Foley, J. P. et al.., Electrophoresis, DOI: 10.1002/elps.200600551). Six stereochemical combinations of dodecoxycarbonylvaline (DDCV: R, S, or racemic, 2.00% w/v), racemic 2-hexanol (1.65% v/v), and diethyl tartrate (D, L, or racemic, 0.88% v/v) were examined as pseudostationary phases (PSPs) for the enantioseparation of six chiral pharmaceutical compounds: pseudoephedrine, ephedrine, N-methyl ephedrine, metoprolol, synephrine, and atenolol. Average efficiencies increased with the addition of a chiral oil to R-DDCV PSP formulations. Modest improvements in resolution and enantioselectivity (alpha(enant)) were achieved with two-chiral-component systems over the one-chiral-component microemulsion. Slight enantioselective synergies were confirmed using a thermodynamic model. Results obtained in this study are compared to those obtained in Part 1 as well as those obtained with chiral MEEKC using an achiral, low-interfacial-tension oil (ethyl acetate). Dual-chirality microemulsions with the more hydrophobic oil dibutyl tartrate yielded, relative to diethyl tartrate, higher efficiencies (100,000-134,000 vs. 80,800-94,300), but lower resolution (1.64-1.91 vs. 2.08-2.21) due to lower enantioselectivities (1.060-1.067 vs. 1.078-1.081). Atenolol enantiomers could not be separated with the dibutyl tartrate-based microemulsions but were partially resolved using diethyl tartrate microemulsions. A comparable single-chirality microemulsion based on the achiral oil ethyl acetate yielded, relative to diethyl tartrate, lower efficiency (78 300 vs. 91 600), higher resolution (1.99 vs. 1.83), and similar enantioselectivities.

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Section: Introductionmentioning

confidence: 99%

Two‐chiral component microemulsion EKC – chiral surfactant and chiral oil. Part 2: Diethyl tartrate

Kahle

Foley

2007

Electrophoresis

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“…The results indicated that the addition of nonaqueous soluble electrolyte such as sodium acetate and tetraethylammonium perchlorate into the MEEKC run buffer was effective in generating sufficient current (10 mA) for achieving good separations and, importantly, separation selectivities were found to be very different than those obtained with o/w microemulsions (e.g., neutral analytes were not separated in order of their hydrophobicities). And interestingly, a follow-up paper by Broderick et al [43] demonstrated that w/o microemulsions were well suited for the MEEKC separation of a wide range of highly hydrophobic drug compounds, including the analysis of fluticasone propionate (neutral steroids) in nasal spray and UV filters (polyaromatic compounds) in sun tan lotions without the need of carrying out the solvent extraction steps (i.e., simply by dissolving the hydrophobic samples in the w/o microemulsion buffer), and good agreements were obtained in comparison to HPLC results.…”

Section: Highly Hydrophobic Substancesmentioning

confidence: 97%

“…For example, during these past few years, Altria and co-workers [56] have developed MEEKC as a novel method for the determination of folic acid (Vitamin B) in drug tablets and, importantly, proper validations were carried out such that this method was found to be suitable for implementation in routine analysis of folic acid formulations in pharmaceutical laboratories. Also, w/o microemulsions were employed in reverse MEEKC for the optimal separation of a range of water-insoluble compounds in pharmaceutical formulations [43]. …”

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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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“…Subsequent investigations by Fung [78] found that the use of a charge carrier in the microemulsion electrolyte resulted in a more stable current but separations were poor due to degradation of the microemulsion. More recent reports by Altria et al [76] and Broderick et al [1] showed that a microemulsion composition of 10% w/w SDS, 78% w/w butanol, 2% octane and 10% of 0.07 mM sodium acetate aqueous buffer generated a sufficient current to achieve good separations without disruption of the microemulsion caused by variations in temperature and buffer conditions. As well as offering unique selectivities when compared to conventional MEEKC, W/O MEEKC can be used to separate a wide range of hydrophobic compounds without the need for lengthy sample preparation and extraction steps as demonstrated by Broderick et al [1] for the analysis of neutral steroids in a nasal spray and UV filters in sunscreen (see Fig.…”

Section: Water-in-oil Meekcmentioning

confidence: 99%

“…These microemulsions are usually composed of nanometre-sized droplets of hydrophobic organic solvents in an aqueous buffer and are referred to as oil-in-water microemulsions. Although most applications of MEEKC have utilised oil-inwater type microemulsions, there have been a recent applications of water-in-oil MEEKC [1].…”

Section: Introductionmentioning

confidence: 99%

Recent advances in the development and application of microemulsion EKC

et al. 2007

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Microemulsion EKC (MEEKC) is an electrodriven separation technique. Separations are typically achieved using oil-in-water microemulsions, which are composed of nanometre-sized oil droplets suspended in an aqueous buffer. The droplets are stabilised by a surfactant and a cosurfactant. The novel use of water-in-oil microemulsions has also been investigated. This review summarises the advances in the development of MEEKC separations and also the different areas of application including determination of log P values, pharmaceutical applications, chiral analysis, natural products and bioanalytical separations and the use of new methods such as multiplexed MEEKC and high speed MEEKC. Recent applications (2004-2006) are tabulated for each area with microemulsion composition details.

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Optimisation and use of water-in-oil MEEKC in pharmaceutical analysis

Cited by 24 publications

References 20 publications

Two‐chiral component microemulsion EKC – chiral surfactant and chiral oil. Part 2: Diethyl tartrate

Two‐chiral component microemulsion EKC – chiral surfactant and chiral oil. Part 2: Diethyl tartrate

Recent applications of microemulsion electrokinetic chromatography

Recent advances in the development and application of microemulsion EKC

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