Enantiomeric separations of benzodiazepines by electrochemically modulated liquid chromatography

Wang, Songjie; Porter, Marc D.

doi:10.1016/s0021-9673(98)00701-8

Cited by 24 publications

(6 citation statements)

References 46 publications

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“…The electrochemistry of ferri-/ferrocyanide is also consistent with this charge repulsion idea whereby the CV waves are attributable primarily to electrolysis at the outer cylindrical surface of UHSAFCs . There are many examples in the literature, particularly dealing with Nafion-coated electrodes, where there is partitioning or rejection of species depending on the charge or size of the species and the solution pH. − Partitioning into porous microparticles of carbon has also been utilized for liquid chromatographic separations of various species. − …”

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confidence: 74%

Electrochemical Flow Injection Analysis Study of Ion Partitioning at High Surface Area Carbon Fiber Electrodes

et al. 2002

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Charge-selective electrochemistry was previously shown to occur at high surface area carbon fibers that were produced by fracturing the outer periphery with anodic current or positive potential. The cyclic voltammetric behavior of electroactive species observed at these fibers exhibited a distinct pH dependence related to the protonation/deprotonation of oxygen-containing functional groups at the surface of the carbon fiber. In this paper, electrochemical flow injection analysis (EC-FIA) is used to probe ion partitioning in to and out of the interior microstructure of the treated carbon fiber, for both electroactive and electroinactive species. It was found that the extent of partitioning was the result of both ion charge and hydrated ionic radius, in addition to the level of fracture. It was further observed that the direction of movement for an injected ionic species could be controlled relative to the ion concentration, the pH of the carrier solution, or both. EC-FIA allowed the simultaneous observation of current due to ion movement and that due to electron transfer to a redox-active species. The results presented are consistent with a model in which fixed negatively charged sites in the interior of fractured fibers govern ion partitioning with positively charged ions in the carrier solution, with counterions located in the interior "free" volume.

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confidence: 74%

Electrochemical Flow Injection Analysis Study of Ion Partitioning at High Surface Area Carbon Fiber Electrodes

et al. 2002

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“…In our laboratory, − we have been taking advantage of another property of PGCits intrinsic conductivityin exploring the range and scope of electrochemically modulated liquid chromatography (EMLC) as an intriguing variant to LC. − EMLC works by altering analyte retention through the changes in the donor−acceptor properties that result from manipulating the potential applied to a conductive stationary phase like PGC. Thus, EMLC provides a means to enhance the efficiency of a separation without the use of the gradient elution strategies often required by LC to address the analysis of complex samples.…”

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confidence: 99%

“…Thus, EMLC provides a means to enhance the efficiency of a separation without the use of the gradient elution strategies often required by LC to address the analysis of complex samples. We have shown, for example, that EMLC can be readily applied to the separation of mixtures ranging from structurally similar corticosteroids 11 to racemates of important pharmaceutical agents . The advantages of the on-line coupling with electrospray mass spectrometry (ES-MS) have also recently been demonstrated in a collaboration with Van Berkel's group.…”

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confidence: 99%

Chemical Modification of Carbonaceous Stationary Phases by the Reduction of Diazonium Salts

et al. 2001

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This paper describes a new strategy for the creation of chemically modified carbonaceous stationary phases. The strategy exploits the electroreduction of arenediazonium salts as a means for functionalizing the surface of glassy carbon (GC) and porous graphitic carbon (PGC) stationary phases. The one-electron reduction of these salts forms an arene radical which then couples via a carbon-carbon linkage to the carbon framework at the surface of the stationary phase. Two arenediazonium-based modifiers were used in evaluating the potential utility of this strategy: 4-nitrobenzenediazonium tetrafluoroborate for the GC and PGC phases and 4-hexylbenzenediazonium tetrafluoroborate for only the PGC phases. Modifications were carried out by packing the phases into a column used for electrochemically modulated liquid chromatography. The effectiveness of the modifications was assessed by X-ray photoelectron spectroscopy and by comparing the liquid separation of a series of mixtures before and after coating deposition. For the nitrobenzyl-modified GC phase, the test mixture contained both anisole and fluoranthene. The performance of the nitrobenzyl- and hexylbenzyl-modified PGC stationary phases was characterized by the separations of substituted phenols (i.e., nitrophenol and resorcinol) and a few important pharmaceutical agents (i.e., hexobarbital, oxazepam, and nitrazepam). The potential utility of this modification procedure to form stationary phases that are stable upon extended exposure to aggressive mobile phases is discussed and briefly examined.

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“…Wang and Porter [18] used eletrochemically modulated liquid chromatography for the enantiomeric separation of oxazepam, lorazepam and temazepam using a porous graphitic carbon stationary phase and ␤-cyclodextrin as a chiral mobile phase additive. The mobile phase consisted of a mixture of 75% water (0.1 M LiCLO 4 , 6 mM ␤-CD, 20 mM phosphate buffer, pH ∼ 1.8) and 25% acetonitrile (0.1 M LiCLO 4 ).…”

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confidence: 99%

Quantitative assay of lorazepam and its metabolite glucuronide by reverse-phase liquid chromatography-tandem mass spectrometry in human plasma and urine samples

Papini

Bertucci

Cunha

et al. 2006

Journal of Pharmaceutical and Biomedical Analysis

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Enantiomeric separations of benzodiazepines by electrochemically modulated liquid chromatography

Cited by 24 publications

References 46 publications

Electrochemical Flow Injection Analysis Study of Ion Partitioning at High Surface Area Carbon Fiber Electrodes

Electrochemical Flow Injection Analysis Study of Ion Partitioning at High Surface Area Carbon Fiber Electrodes

Chemical Modification of Carbonaceous Stationary Phases by the Reduction of Diazonium Salts

Quantitative assay of lorazepam and its metabolite glucuronide by reverse-phase liquid chromatography-tandem mass spectrometry in human plasma and urine samples

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