Combined liquid-liquid electroextraction-isotachophoresis for loadability enhancement in capillary zone electrophoresis-mass spectrometry

Vlis, E. van der; Mazereeuw, M.; Tjaden, U.R.; Irth, H.; Greef, J. van der

doi:10.1016/0021-9673(95)00366-u

Cited by 44 publications

(25 citation statements)

References 23 publications

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“…In the final step (F), the capillary inlet is placed into the leading buffer and CZE is started by application of separation voltage. The method has been applied to preconcentration and determination of compounds of pharmaceutical relevance in standard solutions [19][20][21], applications to real biological samples were, however, not Generalshown in these papers. EE was also presented as a suitable pretreatment and preconcentration technique for HPLC [21].…”

Section: Systems With Two Immiscible Solventsmentioning

confidence: 96%

“…LiquidÀliquid EE in combination with capillary ITP was presented as an on-line focusing technique for CZE in [19,20]. LiquidÀliquid EE is used to focus the analyte ions from a large organic sample into a small volume in a terminating buffer zone, just above the liquidÀliquid interface.…”

Section: Systems With Two Immiscible Solventsmentioning

confidence: 99%

“…The convective mixing, which often accompanies the LLE, was suppressed since the thermal flows could not cross the phase interfaces. LiquidÀliquid EE has later been used as a sample preparation technique in CE and LC [19][20][21]. In order to allow the electric current to flow through the two immiscible liquid phases, the non-conductive organic phase was saturated with ionic species and EE was applied as a fast on-line sample pretreatment step for the two separation methods.…”

Section: Introductionmentioning

confidence: 99%

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Electric field‐enhanced transport across phase boundaries and membranes and its potential use in sample pretreatment for bioanalysis

2010

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Separation techniques, such as electrodialysis, electroextraction, electro-membrane extraction and extraction across phase interfaces, are reviewed and discussed as methods for sample cleanup and preconcentration. This survey clearly shows that electromigration of ionic species across phase interfaces, especially across supported liquid membranes, may be very selective and is strongly dependent on the chemical composition of these interfaces. Thus, electric field-enhanced transport across chemically tailored liquid membranes may open new perspectives in preparative analytical chemistry. This review offers comprehensive survey of related literature and discussion of the topic, which may stimulate interest of experts and practitioners in bioanalysis.

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Section: Systems With Two Immiscible Solventsmentioning

confidence: 96%

Section: Systems With Two Immiscible Solventsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electric field‐enhanced transport across phase boundaries and membranes and its potential use in sample pretreatment for bioanalysis

2010

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“…In principle, the electrospray process also does not require a large amount of methanol. However, methanol was added to improve both the separation of the three -agonists 23 and the spray conditions, the latter due to reduction of the surface tension of the electrolyte. 24 By narrowing the capillary tip, local differences in the electrical resistance will be produced.…”

Section: Capillary Zone Electrophoresis/mass Spectrometrymentioning

confidence: 99%

A novel sheathless and electrodeless microelectrospray interface for the on-line coupling of capillary zone electrophoresis to mass spectrometry

Mazereeuw

Hofte

Tjaden

et al. 1997

Rapid Commun. Mass Spectrom.

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A novel microelectrospray interface for the on-line coupling of capillary-zone electrophoresis (CZE) and mass spectrometry is described. The outlet of the fused-silica CZE capillary is tapered and serves as the microspray tip. The spray does not contain a sheath flow nor does the capillary tip contain an electrode or a conductive coating. The capillary tip is placed directly in front of the mass spectrometer inlet. The electrical field for the CZE separation as well as for the electrospray is delivered by the CZE high-voltage power supply. The electrical contact at the capillary outlet is established through the air between the spray tip and the inlet of the mass spectrometer, which is at ground potential.The performance of this interface is investigated using several -agonists, which are low-molecular-weight, cationic drugs, as test compounds. The combination of capillary electrophoresis (CZE) and mass spectrometry offers high separation power with a highly compound-selective and universally applicable detection technique.1,2 CZE/MS interfacing is generally performed using electrospray ionization (ESI) and its application has been successfully demonstrated for a broad range of compounds. 3,4 Since the introduction of ESI as a CZE/MS interface, 5 the interface has mainly been operated with a coaxial sheath liquid to establish the electrical contact and adjustment of the spray and ionization conditions. However, the presence of additional ions in the sheath flow can reduce the detectability of the analytes. 6 The sheath liquid is delivered with a flow of several microlitres per minute via a stainless steel capillary, which surrounds the CZE capillary terminus. A different approach has been presented, in which a liquid junction was used to establish the electrical contact and to add a make-up flow before the capillary terminus. The diameter of the formed droplets depends on the flow of the sheath liquid 8,9 and influences the evaporation efficiency of the droplets and, therefore, affects the amount of ions entering the mass spectrometer. Reduction of the flow can be obtained by removing the sheath flow and spraying the CZE capillary content directly into the mass spectrometer as has already been demonstrated. [10][11][12][13][14][15][16] In this approach, the electrical contact is made either via a metal coating at the capillary tip [10][11][12][13][14][15] or by inserting a narrow metal wire into the outlet of the capillary. 16 Although a metal coating functions properly as an electrode, a coating apparatus is necessary and in several cases flaking of the coating is reported during electrospraying. The use of a metal wire as an outlet electrode, although reported to be successful by Zare et al., 16 in our experience does not always result in a stable spray.Micro-or nanospray systems have gained recently a lot of interest, because of the low flow rate and the high electrospray efficiency. 8,9,17,18 Moreover, a microspray is very stable due to the small surface from which the spray originates and allows the use of...

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“…Van der Greef et al reported early attempts of analytical EE in the period 1994 -1996. [3][4][5] Three research papers demonstrated EE of charged substances from an organic solvent (ethyl acetate) and into aqueous solutions for subsequent analysis by CE or HPLC. Thus, conventional LLE was performed prior to EE when the technique was used for aqueous samples such as biological fluids.…”

Section: Introductionmentioning

confidence: 99%

Electromembrane Extraction from Biological Fluids

et al. 2011

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Combined liquid-liquid electroextraction-isotachophoresis for loadability enhancement in capillary zone electrophoresis-mass spectrometry

Cited by 44 publications

References 23 publications

Electric field‐enhanced transport across phase boundaries and membranes and its potential use in sample pretreatment for bioanalysis

Electric field‐enhanced transport across phase boundaries and membranes and its potential use in sample pretreatment for bioanalysis

A novel sheathless and electrodeless microelectrospray interface for the on-line coupling of capillary zone electrophoresis to mass spectrometry

Electromembrane Extraction from Biological Fluids

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