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Zhang R, Liu W, Luan Z, Xia Y, Wang Y, Hu X, Duraihem FZ, Xu X. Effects of the Electric Double Layer Characteristic and Electroosmotic Regulation on the Tribological Performance of Water-Based Cutting Fluids. MICROMACHINES 2023; 14:2029. [PMID: 38004886 PMCID: PMC10673424 DOI: 10.3390/mi14112029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 10/25/2023] [Accepted: 10/27/2023] [Indexed: 11/26/2023]
Abstract
The electroosmosis effect is a complement to the theory of the traditional capillary penetration of cutting fluid. In this study, based on the electric double layer (EDL) characteristics at friction material/solution interfaces, the influences of additives and their concentrations on capillary electroosmosis were investigated, and a water-based cutting-fluid formulation with consideration to the electroosmosis effect was developed. The lubrication performance levels of cutting fluids were investigated by a four-ball tribometer. The results show that the EDL is compressed with increasing ionic concentration, which suppresses the electroosmotic flow (EOF). The specific adsorption of OH- ions or the dissociation of surface groups is promoted as pH rises, increasing the absolute zeta potential and EOF. The polyethylene glycol (PEG) additive adsorbed to the friction material surface can keep the shear plane away from the solid surface, reducing the absolute zeta potential and EOF. The electroosmotic performance of cutting fluid can be improved by compounding additives with different electroosmotic performance functions. Furthermore, electroosmotic regulators can adjust the zeta potential by the electrostatic adsorption mechanism, affecting the penetration performance of cutting fluid in the capillary zone at the friction interface. The improvement in the tribological performance of cutting fluid developed with consideration given to the electroosmosis effect is attributed to the enhancement of the penetration ability of the cutting fluid and the formation of more abundant amounts of lubricating film at the interface.
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Affiliation(s)
- Ruochong Zhang
- College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310023, China; (R.Z.); (W.L.); (Z.L.); (Y.X.); (Y.W.); (X.H.)
- Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education and Zhejiang Province, Zhejiang University of Technology, Hangzhou 310023, China
| | - Wenshuai Liu
- College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310023, China; (R.Z.); (W.L.); (Z.L.); (Y.X.); (Y.W.); (X.H.)
- Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education and Zhejiang Province, Zhejiang University of Technology, Hangzhou 310023, China
| | - Zhiqiang Luan
- College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310023, China; (R.Z.); (W.L.); (Z.L.); (Y.X.); (Y.W.); (X.H.)
- Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education and Zhejiang Province, Zhejiang University of Technology, Hangzhou 310023, China
| | - Yu Xia
- College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310023, China; (R.Z.); (W.L.); (Z.L.); (Y.X.); (Y.W.); (X.H.)
- Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education and Zhejiang Province, Zhejiang University of Technology, Hangzhou 310023, China
| | - Ying Wang
- College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310023, China; (R.Z.); (W.L.); (Z.L.); (Y.X.); (Y.W.); (X.H.)
- Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education and Zhejiang Province, Zhejiang University of Technology, Hangzhou 310023, China
| | - Xiaodong Hu
- College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310023, China; (R.Z.); (W.L.); (Z.L.); (Y.X.); (Y.W.); (X.H.)
- Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education and Zhejiang Province, Zhejiang University of Technology, Hangzhou 310023, China
| | - Faisal Z. Duraihem
- Department of Mathematics, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia;
| | - Xuefeng Xu
- College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310023, China; (R.Z.); (W.L.); (Z.L.); (Y.X.); (Y.W.); (X.H.)
- Key Laboratory of Special Purpose Equipment and Advanced Processing Technology, Ministry of Education and Zhejiang Province, Zhejiang University of Technology, Hangzhou 310023, China
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2
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Barbosa FHB, Quero RF, Rocha KN, Costa SC, de Jesus DP. Electroosmotic flow in fused deposition modeling (FDM) 3D-printed microchannels. Electrophoresis 2023; 44:558-562. [PMID: 36495094 DOI: 10.1002/elps.202200211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 11/26/2022] [Accepted: 12/05/2022] [Indexed: 12/14/2022]
Abstract
Electroosmotic flow (EOF) was determined in tridimensional (3D)-printed microchannels with dimensions smaller than 100 µm. Fused deposition modeling 3D printing using thermoplastic filaments of PETG (polyethylene terephthalate glycol), PLA (polylactic acid), and ABS (acrylonitrile butadiene styrene) were used to fabricate the microchannels. The current monitoring method and sodium phosphate solutions at different pH values (3-10) were used for the EOF mobility (µEOF ) measurements, which ranged from 2.00 × 10-4 to 12.52 × 10-4 cm2 V-1 s-1 . The highest and the smallest µEOF were obtained for the PLA and PETG microchannels, respectively. Adding the cationic surfactant cetyltrimethylammonium bromide to the sodium phosphate solution caused EOF direction reversion in all the studied microchannels. The obtained results can be interesting for developing 3D-printed microfluidic devices, in which EOF is relevant.
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Affiliation(s)
| | | | | | | | - Dosil Pereira de Jesus
- Institute of Chemistry, University of Campinas, Campinas, São Paulo, Brazil.,Instituto Nacional de Ciência e Tecnologia de Bioanalítica, Campinas, São Paulo, Brazil
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3
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Vaas APJP, Yu RB, Quirino JP. In-line sample concentration in capillary electrophoresis by cyclodextrin to admicelle microextraction. Anal Bioanal Chem 2022; 414:6671-6680. [PMID: 35978220 PMCID: PMC9411250 DOI: 10.1007/s00216-022-04230-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 07/08/2022] [Accepted: 07/13/2022] [Indexed: 11/25/2022]
Abstract
Cyclodextrins (CDs) as a pseudophase in pseudophase-to-pseudophase microextraction (P2ME) in capillary zone electrophoresis (CZE) are proposed. In this P2ME mode called CD to admicelle ME, a long plug of dilute analyte solution prepared in cetyltrimethylammonium bromide (CTAB) at the critical micellar concentration was injected into the capillary. This formed CTAB admicelles at the interface between the solution and the negatively charged capillary surface, where the analytes were trapped. The injection of CD solution released the admicelles and the analytes from the capillary surface due to the formation of stable CD/CTAB inclusion complexes. The analytes are concentrated at the CD front during injection and voltage separation. Various neutral CDs were found to be effective for CD to admicelle ME. To implement this in-line sample concentration technique in CZE, CD concentration, sample injection time, and sample:CD solution injection ratio were optimized. The optimized conditions for five model anionic analytes, namely, 4-bromophenol, sulindac, sulfamethizole, 4-vinylbenzoic acid, and succinylsulfathiazole, were 20 mM α-CD in 20 mM sodium tetraborate (pH 9.2) solution, sample injection time of 370 s, and CD:sample injection ratio of 1:2. The sensitivity enhancement factors (SEFs) were between 112 and 168. The SEFs of sulindac and sulfamethizole in particular were similar to previously published off-line microextraction techniques, which are typically time-consuming. The calculated values of LOQ, intra-/inter-day (n = 6/n = 10, 3 days) repeatability, and linearity (R2) of CD to admicelle ME were 0.0125-0.05 µg/mL, 1.5-4.6%, 1.8-4.8%, and ≥0.999, respectively. Finally, the potential of CD to admicelle ME to the analysis of artificial urine samples was demonstrated.
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Affiliation(s)
- Andaravaas Patabadige Jude P Vaas
- Australian Centre for Research On Separation Science (ACROSS), School of Natural Sciences-Chemistry, University of Tasmania, Private Bag 75, Hobart, TAS, 7001, Australia
| | - Raymond B Yu
- Australian Centre for Research On Separation Science (ACROSS), School of Natural Sciences-Chemistry, University of Tasmania, Private Bag 75, Hobart, TAS, 7001, Australia.,Department of Pharmaceutical Chemistry, College of Pharmacy, University of the Philippines Manila, Manila, Philippines
| | - Joselito P Quirino
- Australian Centre for Research On Separation Science (ACROSS), School of Natural Sciences-Chemistry, University of Tasmania, Private Bag 75, Hobart, TAS, 7001, Australia.
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Effects of an Electrical Double Layer and Tribo-Induced Electric Field on the Penetration and Lubrication of Water-Based Lubricants. LUBRICANTS 2022. [DOI: 10.3390/lubricants10060111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Understanding the effects of electrical double layers (EDL) and tribo-induced electric fields on the electroosmotic behaviors of lubricants is important for developing high-performance water-based lubricants. In this study, EDL conductivities of aqueous lubricants containing a surfactant of 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) or cetyltrimethylammonium bromide (CTAB) were analyzed. The interfacial zeta potentials of the synthesized lubricants and Al2O3 ceramic-alloy steel contacts were measured, and frictional potentials of ceramic and steel surfaces were determined using a modified ball-on-disc configuration. The distribution characteristics of the tribo-induced electric field of the ceramic-steel sliding contact were numerically analyzed. The electroosmotic behaviors of the lubricants were investigated using a four-ball configuration. It was found that an EDL and tribo-induced electric field was a crucial enabler in stimulating the electroosmosis of lubricants. Through altering EDL structures, CHAPS enhanced the electroosmosis and penetration of the water-based lubricant, thus resulting in improved lubrication.
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Cyclodextrins as mobile phase additives in open-tubular admicellar electrochromatography for achiral and chiral separations. Microchem J 2021. [DOI: 10.1016/j.microc.2020.105763] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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6
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Jia Y, Cao J, Zhou J, Zhou P. Methyl chitosan coating for glycoform analysis of glycoproteins by capillary electrophoresis. Electrophoresis 2020; 41:729-734. [DOI: 10.1002/elps.201900333] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 01/09/2020] [Accepted: 01/15/2020] [Indexed: 02/06/2023]
Affiliation(s)
- Yaru Jia
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education)College of Chemistry and Molecular SciencesWuhan University Wuhan P. R. China
| | - Jinfeng Cao
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education)College of Chemistry and Molecular SciencesWuhan University Wuhan P. R. China
| | - Jinping Zhou
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education)College of Chemistry and Molecular SciencesWuhan University Wuhan P. R. China
| | - Ping Zhou
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education)College of Chemistry and Molecular SciencesWuhan University Wuhan P. R. China
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Crihfield C, Kristoff C, Veltri L, Penny W, Holland L. Semi-permanent cationic coating for protein separations. J Chromatogr A 2019; 1607:460397. [DOI: 10.1016/j.chroma.2019.460397] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 06/17/2019] [Accepted: 07/22/2019] [Indexed: 12/16/2022]
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8
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Polak B, Traczuk A, Misztal S. Separation of 9-Fluorenylmethyloxycarbonyl Amino Acid Derivatives in Micellar Systems of High-Performance Thin-Layer Chromatography and Pressurized Planar Electrochromatography. Sci Rep 2019; 9:17103. [PMID: 31745145 PMCID: PMC6864085 DOI: 10.1038/s41598-019-53468-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 10/31/2019] [Indexed: 11/15/2022] Open
Abstract
The problems with separation of amino acid mixtures in reversed-phase mode are the result of their hydrophilic nature. The derivatisation of the amino group of mentioned above solutes leads to their solution. For this purpose, 9-fluorenylmethoxycarbonyl chloroformate (f-moc-Cl) as the derivatisation reagent is often used. In our study, the separation of some f-moc- amino acid derivatives (alanine, phenylalanine, leucine, methionine, proline and tryptophan) with the use of micellar systems of reversed-phase high-performance thin-layer chromatography (HPTLC) and pressurized planar electrochromatography (PPEC) is investigated. The effect of surfactant concentration, its type (anionic, cationic and non-ionic) and mobile phase buffer pH on the discussed above solute migration distances are presented. Our work reveals that the increase of sodium dodecylsulphate concentration in the mobile phase has a different effect on solute retention in HPTLC and PPEC. Moreover, it also affects the order of solutes in both techniques. In PPEC, in contrast to the HPTLC technique, the mobile phase pH affects solute retention. The type of surfactant in the mobile phase also impacts solute retention and migration distances. A mobile phase containing SDS improves system efficiency in both techniques. Herein, such an effect is presented for the first time.
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Affiliation(s)
- Beata Polak
- Department of Physical Chemistry, Medical University of Lublin, Chodźki 4a, 20-093, Lublin, Poland.
| | - Adam Traczuk
- Department of Physical Chemistry, Medical University of Lublin, Chodźki 4a, 20-093, Lublin, Poland
| | - Sylwia Misztal
- Department of Physical Chemistry, Medical University of Lublin, Chodźki 4a, 20-093, Lublin, Poland
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9
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pH-dependent surface properties of the gallium nitride – Solution interface mapped by surfactant adsorption. J Colloid Interface Sci 2019; 556:680-688. [DOI: 10.1016/j.jcis.2019.08.079] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 08/20/2019] [Accepted: 08/21/2019] [Indexed: 11/18/2022]
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10
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Tarongoy F, Haddad PR, Quirino JP. Admicelles in open-tube capillaries for chromatography and electrochromatography. Anal Chim Acta 2019; 1067:147-154. [PMID: 31047146 DOI: 10.1016/j.aca.2019.03.037] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 03/15/2019] [Accepted: 03/16/2019] [Indexed: 12/15/2022]
Abstract
Surfactant bilayers or admicelles at the solid surface-liquid interface inside 50-200 μm inner diameter (i.d.) open-tube fused-silica capillaries were developed as 'soft' stationary pseudophases for the liquid chromatographic (LC) separations of neutral and charged analytes. Admicelles were formed in-situ from buffered aqueous mobile phases with cetytrimethylammonium bromide at concentrations between the critical surface aggregation concentration and critical micelle concentration, which were determined by electroosmotic flow measurements using capillary electrophoresis. There were no micelles in the mobile phase solution. Also, there was no solid phase that is classically required in LC. Pressure and voltage driven modes or open-tubular admicellar liquid chromatography (OT-AMLC) and electrochromatography, respectively were proposed based on the separation of neutral analytes. The parameters (i.e., pH, concentration of surfactant, salt, and methanol in the mobile phase and capillary i.d.) that affected the surprising chromatographic effect of admicelles at the interface were investigated. The analytical performance of OT-AMLC for small molecules were found acceptable. Applications to environmental water and biological (HepG cell line metabolism media) samples analysis with appropriate sample preparation procedures were also conducted. The use of pseudophases at the solid surface-liquid interface could be a viable solution to problems associated with the use of solid stationary or support materials in nano- and micro-liquid chromatography and electrochromatography.
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Affiliation(s)
- Faustino Tarongoy
- Australian Centre for Research on Separation Science (ACROSS), School of Natural Sciences-Chemistry, University of Tasmania, Hobart, Tasmania, 7001, Australia
| | - Paul Raymond Haddad
- Australian Centre for Research on Separation Science (ACROSS), School of Natural Sciences-Chemistry, University of Tasmania, Hobart, Tasmania, 7001, Australia
| | - Joselito P Quirino
- Australian Centre for Research on Separation Science (ACROSS), School of Natural Sciences-Chemistry, University of Tasmania, Hobart, Tasmania, 7001, Australia.
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11
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Shulman L, Pei L, Bahnasy MF, Lucy CA. High pH instability of quaternary ammonium surfactant coatings in capillary electrophoresis. Analyst 2018; 142:2145-2151. [PMID: 28524193 DOI: 10.1039/c7an00330g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The two-tailed cationic surfactant dioctadecyldimethyl ammonium bromide (DODAB) produces semi-permanent coatings that yield strongly reversed electroosmotic flow (EOF), for example -0.31 ± 0.01 cm2 kV-1 s-1 at pH 3.5. Moreover, these coatings are easy to prepare, regenerable, cost effective, and yield high efficiency (520 000-900 000 plates per m) separations of cationic proteins over many runs under acidic (pH 3.5) conditions. Given the quaternary amine functionality of DODAB, we were surprised to observe that DODAB coatings become unstable at pH > 7. At pH 7.2, the EOF of a DODAB coated capillary drifted from reversed to cathodic over only 5 runs, and protein separations became severely compromised. By pH 12, no EOF reversal was observed. Electrophoretic and mass spectrometric studies demonstrate that the coating decomposition involves a surface conversion of the quaternary amine in DODAB to a variety of products, although the exact mechanism remains elusive. Regardless, the results herein demonstrate that semi-permanent coatings based on cationic two-tailed surfactants such as DODAB are limited to separations using acidic buffers.
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Affiliation(s)
- Lisa Shulman
- Department of Chemistry, Gunning/Lemieux Chemistry Centre, University of Alberta, Edmonton, AB, Canada T6G 2G2.
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12
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Determination of neutral diols and carboxylic acids formed during glycerol electrooxidation by capillary electrophoresis with dual C4D. Talanta 2018; 178:1040-1045. [DOI: 10.1016/j.talanta.2017.08.088] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 08/25/2017] [Accepted: 08/28/2017] [Indexed: 11/27/2022]
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Turning bubbles on and off during boiling using charged surfactants. Nat Commun 2015; 6:8599. [PMID: 26486275 PMCID: PMC4639814 DOI: 10.1038/ncomms9599] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 09/09/2015] [Indexed: 12/02/2022] Open
Abstract
Boiling—a process that has powered industries since the steam age—is governed by bubble formation. State-of-the-art boiling surfaces often increase bubble nucleation via roughness and/or wettability modification to increase performance. However, without active in situ control of bubbles, temperature or steam generation cannot be adjusted for a given heat input. Here we report the ability to turn bubbles ‘on and off' independent of heat input during boiling both temporally and spatially via molecular manipulation of the boiling surface. As a result, we can rapidly and reversibly alter heat transfer performance up to an order of magnitude. Our experiments show that this active control is achieved by electrostatically adsorbing and desorbing charged surfactants to alter the wettability of the surface, thereby affecting nucleation. This approach can improve performance and flexibility in existing boiling technologies as well as enable emerging or unprecedented energy applications. Bubble generation during boiling is essential to power generation and heating/cooling systems, but it remains uncontrollable even with state-of-the-art surface engineering. Cho et al. electrostatically attract surfactants to the surface, on which bubble nucleation is manipulated in an on-demand manner.
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15
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Simultaneous separation of acidic and basic proteins using gemini pyrrolidinium surfactants and hexafluoroisopropanol as dynamic coating additives in capillary electrophoresis. J Chromatogr A 2015; 1412:151-8. [DOI: 10.1016/j.chroma.2015.08.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 08/08/2015] [Accepted: 08/10/2015] [Indexed: 11/18/2022]
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16
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Huang D, Yang Q, Jin S, Deng Q, Zhou P. Self-assembly of cellulose nanoparticles as electrolyte additive for capillary electrophoresis separation. J Chromatogr A 2014; 1367:148-53. [DOI: 10.1016/j.chroma.2014.09.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 09/11/2014] [Accepted: 09/14/2014] [Indexed: 12/30/2022]
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17
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Liu Y, Shamsi SA. Combined use of chiral ionic liquid surfactants and neutral cyclodextrins: evaluation of ionic liquid head groups for enantioseparation of neutral compounds in capillary electrophoresis. J Chromatogr A 2014; 1360:296-304. [PMID: 25130088 DOI: 10.1016/j.chroma.2014.07.047] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Revised: 07/07/2014] [Accepted: 07/16/2014] [Indexed: 11/15/2022]
Abstract
Cyclodextrins (CDs) are most commonly used chiral selectors in capillary electrophoresis (CE). Although the use of neutral CDs and its derivatives have shown to resolve plethora of charged enantiomers, they cannot resolve neutral enantiomers. The use of ionic liquids (ILs) surfactants forming successful complex with CDs present itself an opportunity to resolve neutral enantiomers. In this work, the effect of IL head groups and their complexation ability with heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD) was studied for the separation of neutral enantiomers by CE. First, cationic IL type surfactants with different chiral head groups were synthesized. Physicochemical properties such as critical micelle concentration were determined by surface tension, whereas aggregation and polarity were determined by fluorescence spectroscopy. The complexation ability of ILs with TM-β-CD was characterized in the gas phase by CE-mass spectrometry. The influence of the type of ILs head group and its concentration on chiral resolution, resolution per unit time and selectivity were investigated for four structurally diverse neutral compounds. The binding constants of the neutral analytes to the IL-CD complex were estimated by y-reciprocal method. The hydrophobicity of the side chain of the IL head group displayed significant effect on the binding constants and enantioseparations.
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Affiliation(s)
- Yijin Liu
- Department of Chemistry, Center of Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, United States
| | - Shahab A Shamsi
- Department of Chemistry, Center of Diagnostics and Therapeutics, Georgia State University, Atlanta, GA 30303, United States.
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Barbati AC, Kirby BJ. Electrokinetic measurements of thin Nafion films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:1985-1993. [PMID: 24479374 DOI: 10.1021/la403735g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We perform an electrokinetic characterization of ~300 nm Nafion films deposited on glass slides over a relatively unexplored region of ionic strength and pH. Owing to the small pore size of the Nafion, we probe the Nafion-fluid interface with the streaming potential measurement, and we probe ionic transport through the entire thickness of the Nafion film with the conductivity measurements. By applying a transport model for each of these measurements, we show that the inferred fixed charge density and characteristic fluid resistance length is different in each case. Analyzing our results with data from the literature, we suggest that our result is consistent with a thin Nafion film that is both nonuniform and weakly hydrated. Our regimen of experimentation and analysis may be generalized to characterize other porous and charged layers.
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Affiliation(s)
- Alexander C Barbati
- Sibley School of Mechanical and Aerospace Engineering, Cornell University , Ithaca, New York 14853, United States
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Barbati AC, Kirby BJ. Force and flux relations for flows of ionic solutions between parallel plates with porous and charged layers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:042408. [PMID: 24229190 DOI: 10.1103/physreve.88.042408] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Indexed: 06/02/2023]
Abstract
We derive coefficients of the electrokinetic coupling matrix (χ(11), χ(12), and χ(21)) for the flow of an ionic solution through a parallel-plate geometry having porous and charged layers grafted onto a solid surface with a known potential and demonstrate Onsager reciprocity for the cross terms (i.e., χ(12)=χ(21)). Our results enable the prediction of system outputs in the solid-porous-fluid system from parameters that are either known or may be measured and inferred. These electrokinetic coupling coefficients are in terms of the potential, ϕ, and fixed charge, ρ(f), only, removing dependence on field gradients and fluid velocity. Additionally, we present simplified expressions of these coupling coefficients in limiting regions of the parameter space. Away from these limits, we present numerical results demonstrating the facility of our functional form for facile numerical approximation and report the utility and accuracy of our analytical approximations.
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Affiliation(s)
- Alexander C Barbati
- Sibley School of Mechanical and Aerospace Engineering and Cornell University and Ithaca, New York 14853, USA
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Azadi G, Chauhan A, Tripathi A. Dilution of protein-surfactant complexes: a fluorescence study. Protein Sci 2013; 22:1258-65. [PMID: 23868358 DOI: 10.1002/pro.2313] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 06/25/2013] [Accepted: 07/08/2013] [Indexed: 11/11/2022]
Abstract
Dilution of protein-surfactant complexes is an integrated step in microfluidic protein sizing, where the contribution of free micelles to the overall fluorescence is reduced by dilution. This process can be further improved by establishing an optimum surfactant concentration and quantifying the amount of protein based on the fluorescence intensity. To this end, we study the interaction of proteins with anionic sodium dodecyl sulfate (SDS) and cationic hexadecyl trimethyl ammonium bromide (CTAB) using a hydrophobic fluorescent dye (sypro orange). We analyze these interactions fluourometrically with bovine serum albumin, carbonic anhydrase, and beta-galactosidase as model proteins. The fluorescent signature of protein-surfactant complexes at various dilution points shows three distinct regions, surfactant dominant, breakdown, and protein dominant region. Based on the dilution behavior of protein-surfactant complexes, we propose a fluorescence model to explain the contribution of free and bound micelles to the overall fluorescence. Our results show that protein peak is observed at 3 mM SDS as the optimum dilution concentration. Furthermore, we study the effect of protein concentration on fluorescence intensity. In a single protein model with a constant dye quantum yield, the peak height increases with protein concentration. Finally, addition of CTAB to the protein-SDS complex at mole fractions above 0.1 shifts the protein peak from 3 mM to 4 mM SDS. The knowledge of protein-surfactant interactions obtained from these studies provides significant insights for novel detection and quantification techniques in microfluidics.
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Affiliation(s)
- Glareh Azadi
- Center for Biomedical Engineering, School of Engineering, Brown University, Providence, Rhode Island, 02912
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21
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Yang H, Ding Y, Cao J, Li P. Twenty-one years of microemulsion electrokinetic chromatography (1991-2012): A powerful analytical tool. Electrophoresis 2013; 34:1273-94. [DOI: 10.1002/elps.201200494] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 12/18/2012] [Accepted: 01/22/2013] [Indexed: 12/18/2022]
Affiliation(s)
- Hua Yang
- State Key Laboratory of Natural Medicines (China Pharmaceutical University); Nanjing; P. R. China
| | - Yao Ding
- State Key Laboratory of Natural Medicines (China Pharmaceutical University); Nanjing; P. R. China
| | - Jun Cao
- College of Material Chemistry and Chemical Engineering; Hangzhou Normal University; Hangzhou; P. R. China
| | - Ping Li
- State Key Laboratory of Natural Medicines (China Pharmaceutical University); Nanjing; P. R. China
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22
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Li X, Chen Z, Yang F, Pan J, Li Y. Development of a microchip-pulsed electrochemical method for rapid determination of L-DOPA and tyrosine inMucuna pruriens. J Sep Sci 2013; 36:1590-6. [DOI: 10.1002/jssc.201300041] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Revised: 03/02/2013] [Accepted: 03/08/2013] [Indexed: 11/10/2022]
Affiliation(s)
| | - Zuanguang Chen
- School of Pharmaceutical Sciences; Sun Yat-sen University; Guangzhou; China
| | - Fan Yang
- Laboratory of Physical Biology; Shanghai Institute of Applied Physics; Chinese Academy of Sciences; Shanghai; China
| | - Jianbin Pan
- School of Pharmaceutical Sciences; Sun Yat-sen University; Guangzhou; China
| | - Yinbao Li
- School of Pharmaceutical Sciences; Sun Yat-sen University; Guangzhou; China
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23
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Yeung KK, Lucy CA. Isotopic separation of [(14)n]- and [(15)n]aniline by capillary electrophoresis using surfactant- controlled reversed electroosmotic flow. Anal Chem 2012; 70:3286-90. [PMID: 21644665 DOI: 10.1021/ac9801566] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Separation of isotopically labeled [(14)N]- and [(15)N]aniline was achieved using capillary electrophoresis based on the isotopic effect on pK(a). The effects of the buffer co-ion, pH, and electroosmotic mobility on the resolution are investigated in this paper. Electroosmotic flow (EOF) was controlled using the zwitterionic surfactant Rewoteric AM CAS U as buffer additive. The resultant EOF was anodic (reversed) and low in magnitude (0.6 × 10(-)(4) cm(2)/(V·s)). The resolution of [(14)N]- and [(15)N]aniline was 1.22. Addition of a cationic surfactant, cetyltrimethylammonium bromide, to the zwitterionic surfactant increased the magnitude of the anodic EOF. This EOF improved the resolution to 1.33 based on mobility counterbalance.
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Affiliation(s)
- K K Yeung
- Department of Chemistry, The University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
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24
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Dynamically formed admicelle layer to control the amplitude of cathodic electroosmotic flow. J Chromatogr A 2012; 1256:271-5. [DOI: 10.1016/j.chroma.2012.07.076] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Revised: 07/20/2012] [Accepted: 07/23/2012] [Indexed: 11/22/2022]
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25
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Azadi G, Tripathi A. Surfactant-induced electroosmotic flow in microfluidic capillaries. Electrophoresis 2012; 33:2094-101. [DOI: 10.1002/elps.201100633] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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26
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27
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Mallah A, Memon SQ, Solangi AR, Memon N, Abbassi K, Khuhawar MY. A Novel Micellar Electrokinetic Chromatographic Method for Separation of Metal-DDTC Complexes. ScientificWorldJournal 2012; 2012:743407. [PMID: 22649320 PMCID: PMC3354655 DOI: 10.1100/2012/743407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 12/13/2011] [Indexed: 11/17/2022] Open
Abstract
Micellar electrokinetic chromatography (MEKC) was examined for the separation and determination of Mo(VI), Cr(VI), Ni(II), Pd(II), and Co(III) as diethyl dithiocarbamate (DDTC) chelates. The separation was achieved from fused silica capillary (52 cm × 75 μm id) with effective length 40 cm, background electrolyte (BGE) borate buffer pH 9.1 (25 mM), CTAB 30% (100 mM), and 1% butanol in methanol (70 : 30 : 5 v/v/v) with applied voltage of −10 kV using reverse polarity. The photodiode array detection was achieved at 225 nm. The linear calibration for each of the element was obtained within 0.16–10 μg/mL with a limit of detection (LOD) 0.005–0.0167 μg/mL. The separation and determination was repeatable with relative standard deviation (RSD) within 2.4–3.3% (n = 4) in terms of migration time and peak height/peak area. The method was applied for the determination of Mo(VI) from potatoes and almond, Ni(II) from hydrogenated vegetable oil, and Co(III) from pharmaceutical preparations with RSD within 3.9%. The results obtained were checked by standard addition and rechecked by atomic absorption spectrometry.
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Affiliation(s)
- Arfana Mallah
- M.A. Kazi Institute of Chemistry, University of Sindh, Jamshoro 76080, Pakistan
| | - Saima Q. Memon
- Institute of Advanced Research Studies in Chemical Sciences, University of Sindh, Jamshoro 76080, Pakistan
| | - Amber R. Solangi
- National Center of Excellence in Analytical Chemistry, University of Sindh, Jamshoro 76080, Pakistan
| | - Najma Memon
- National Center of Excellence in Analytical Chemistry, University of Sindh, Jamshoro 76080, Pakistan
| | - Kulsoom Abbassi
- M.A. Kazi Institute of Chemistry, University of Sindh, Jamshoro 76080, Pakistan
| | - Muhammad Yar Khuhawar
- Institute of Advanced Research Studies in Chemical Sciences, University of Sindh, Jamshoro 76080, Pakistan
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28
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Matsumiya H, Kitakata K, Hiraide M. Collection of trace metals with cationic surfactant-silica particles followed by flotation with an anionic surfactant for seawater analysis. Anal Bioanal Chem 2011; 402:1973-7. [DOI: 10.1007/s00216-011-5608-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 11/22/2011] [Accepted: 11/24/2011] [Indexed: 11/30/2022]
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29
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Huang J, DiStefano J. CHARACTERIZING EFFECTS OF CATIONIC SURFACTANT ON ELECTRO-OSMOTIC MOBILITY AND ANION MIGRATION IN CAPILLARY ELECTROPHORESIS. J LIQ CHROMATOGR R T 2011. [DOI: 10.1080/10826076.2011.578323] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- Jinmo Huang
- a Chemistry Department , The College of New Jersey , Ewing, New Jersey, USA
| | - James DiStefano
- a Chemistry Department , The College of New Jersey , Ewing, New Jersey, USA
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30
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Viefhues M, Manchanda S, Chao TC, Anselmetti D, Regtmeier J, Ros A. Physisorbed surface coatings for poly(dimethylsiloxane) and quartz microfluidic devices. Anal Bioanal Chem 2011; 401:2113-22. [PMID: 21847528 DOI: 10.1007/s00216-011-5301-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 07/22/2011] [Accepted: 07/28/2011] [Indexed: 01/20/2023]
Abstract
Surface modifications of microfluidic devices are of essential importance for successful bioanalytical applications. Here, we investigate three different coatings for quartz and poly(dimethylsiloxane) (PDMS) surfaces. We employed a triblock copolymer with trade name F(108), poly(L-lysine)-g-poly(ethylene glycol) (PLL-PEG), as well as the hybrid coating n-dodecyl-β-D-maltoside and methyl cellulose (DDM/MC). The impact of these coatings was characterized by measuring the electroosmotic flow (EOF), contact angle, and prevention of protein adsorption. Furthermore, we investigated the influence of static coatings, i.e., the incubation with the coating agent prior to measurements, and dynamic coatings, where the coating agent was present during the measurement. We found that all coatings on PDMS as well as quartz reduced EOF, increased reproducibility of EOF, reduced protein adsorption, and improved the wettability of the surfaces. Among the coating strategies tested, the dynamic coatings with DDM/MC and F(108) demonstrated maximal reduction of EOF and protein adsorption and simultaneously best long-term stability concerning EOF. For PLL-PEG, a reversal in the EOF direction was observed. Interestingly, the static surface coating strategy with F(108) proved to be as effective to prevent protein adsorption as dynamic coating with this block copolymer. These findings will allow optimized parameter choices for coating strategies on PDMS and quartz microfluidic devices in which control of EOF and reduced biofouling are indispensable.
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Affiliation(s)
- M Viefhues
- Experimental Biophysics and Applied Nanoscience, Bielefeld University, 33615 Bielefeld, Germany
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31
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Cao F, Luo Z, Zhou D, Zeng R, Wang Y. Hydroxyethylcellulose-graft-poly(2-(dimethylamino)ethyl methacrylate) as physically adsorbed coating for protein separation by CE. Electrophoresis 2011; 32:1148-55. [DOI: 10.1002/elps.201000528] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Revised: 01/10/2011] [Accepted: 01/11/2011] [Indexed: 02/05/2023]
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32
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Shin GW, Hwang HS, Chung B, Jung GY. Recent developments in CE-based detection methods for food-borne pathogens. Electrophoresis 2010; 31:2137-53. [DOI: 10.1002/elps.200900682] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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33
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Breadmore MC. Electroosmotic flow-balanced isotachophoretic stacking with continuous electrokinetic injection for the concentration of anions in high conductivity samples. J Chromatogr A 2010; 1217:3900-6. [DOI: 10.1016/j.chroma.2010.04.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Revised: 03/30/2010] [Accepted: 04/08/2010] [Indexed: 12/28/2022]
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34
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Chen B, Du Y. Evaluation of the enantioseparation capability of the novel chiral selector clindamycin phosphate towards basic drugs by micellar electrokinetic chromatography. J Chromatogr A 2010; 1217:1806-12. [DOI: 10.1016/j.chroma.2010.01.043] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 01/02/2010] [Accepted: 01/14/2010] [Indexed: 11/28/2022]
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35
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Petr J, Ryparová O, Znaleziona J, Maier VÃ, SÌevcÌÃk J. On-line combination of CE and microscopy: An insight into the migration of microorganisms. Electrophoresis 2009; 30:3863-9. [DOI: 10.1002/elps.200900230] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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36
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Separation of amino acids and amines by capillary electrophoresis using poly(ethylene oxide) solution containing cetyltrimethylammonium bromide. J Chromatogr A 2009; 1216:7576-81. [DOI: 10.1016/j.chroma.2009.02.054] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2008] [Revised: 02/13/2009] [Accepted: 02/16/2009] [Indexed: 11/21/2022]
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37
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Han B, Xu Y, Zhang L, Yang X, Wang E. Surface modification of poly(dimethylsiloxane) microchips using a double-chained cationic surfactant for efficiently resolving fluorescent dye adsorption. Talanta 2009; 79:959-62. [DOI: 10.1016/j.talanta.2009.04.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Revised: 04/10/2009] [Accepted: 04/16/2009] [Indexed: 11/24/2022]
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38
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Liu Q, Yang Y, Huang Y, Pan C, Nie Z, Yao S. Separation of acidic and basic proteins by CE with CTAB additive and its applications in peptide and protein profiling. Electrophoresis 2009; 30:2151-8. [DOI: 10.1002/elps.200800785] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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39
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Stutz H. Protein attachment onto silica surfaces - a survey of molecular fundamentals, resulting effects and novel preventive strategies in CE. Electrophoresis 2009; 30:2032-61. [DOI: 10.1002/elps.200900015] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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40
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Jambovane S, Duin EC, Kim SK, Hong JW. Determination of Kinetic Parameters, Km and kcat, with a Single Experiment on a Chip. Anal Chem 2009; 81:3239-45. [PMID: 19338287 DOI: 10.1021/ac8020938] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sachin Jambovane
- Materials Research and Education Center, Department of Mechanical Engineering, Auburn University, Auburn, Alabama 36849, Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, and Marine Bioprocess Research Center, Pukyong National University, Busan, 608-737, Korea
| | - Evert C. Duin
- Materials Research and Education Center, Department of Mechanical Engineering, Auburn University, Auburn, Alabama 36849, Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, and Marine Bioprocess Research Center, Pukyong National University, Busan, 608-737, Korea
| | - Se-Kwon Kim
- Materials Research and Education Center, Department of Mechanical Engineering, Auburn University, Auburn, Alabama 36849, Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, and Marine Bioprocess Research Center, Pukyong National University, Busan, 608-737, Korea
| | - Jong Wook Hong
- Materials Research and Education Center, Department of Mechanical Engineering, Auburn University, Auburn, Alabama 36849, Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, and Marine Bioprocess Research Center, Pukyong National University, Busan, 608-737, Korea
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41
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Liu Q, Yang Y, Yao S. Enhanced stability of surfactant-based semipermanent wall coatings in capillary electrophoresis using oppositely charged surfactant. J Chromatogr A 2008; 1187:260-6. [DOI: 10.1016/j.chroma.2008.02.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Revised: 01/31/2008] [Accepted: 02/04/2008] [Indexed: 10/22/2022]
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42
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Lucy CA, MacDonald AM, Gulcev MD. Non-covalent capillary coatings for protein separations in capillary electrophoresis. J Chromatogr A 2008; 1184:81-105. [DOI: 10.1016/j.chroma.2007.10.114] [Citation(s) in RCA: 252] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2007] [Revised: 10/25/2007] [Accepted: 10/31/2007] [Indexed: 11/27/2022]
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43
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Mohabbati S, Hjertén S, Westerlund D. Studies on the analytical performance of a non-covalent coating with N,N-didodecyl-N,N-dimethylammonium bromide for separation of basic proteins by capillary electrophoresis in acidic buffers in 25-and 50-μm capillaries. Anal Bioanal Chem 2007; 390:667-78. [DOI: 10.1007/s00216-007-1715-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Revised: 10/12/2007] [Accepted: 10/18/2007] [Indexed: 11/27/2022]
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44
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Gong M, Wehmeyer KR, Limbach PA, Heineman WR. Flow manipulation for sweeping with a cationic surfactant in microchip capillary electrophoresis. J Chromatogr A 2007; 1167:217-24. [PMID: 17826787 PMCID: PMC2716996 DOI: 10.1016/j.chroma.2007.08.042] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2007] [Revised: 08/13/2007] [Accepted: 08/16/2007] [Indexed: 11/28/2022]
Abstract
Flow manipulation in sweeping microchip capillary electrophoresis (CE) is complicated by the free liquid communication between channels at the intersection, especially when the electroosmotic flows are mismatched in the main channel. Sweeping in traditional CE with cationic micelles is an effective way to concentrate anionic analytes. However, it is a challenge to transfer this method onto microchip CE because the dynamic coating process on capillary walls by cationic surfactants is interrupted when the sample solution free of surfactants is introduced into the microchip channels. This situation presents a difficulty in the sample loading, injection and dispensing processes. By adding surfactant at a concentration around the critical micelle concentration and by properly designing the voltage configuration, the flows in a microchip were effectively manipulated and this sweeping method was successfully moved to microchip CE using tetradecyltrimethylammonium bromide (TTAB). The sweeping effect of cationic surfactant in the sample solution was discussed theoretically and studied experimentally in traditional CE. The flows in a microchip were monitored with fluorescence imaging, and the injection and sweeping processes were studied by locating the detection point along the separation channel. A detection enhancement of up to 500-fold was achieved for 5-carboxyfluorescein.
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Affiliation(s)
- Maojun Gong
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
| | - Kenneth R. Wehmeyer
- Procter and Gamble Pharmaceuticals, Health Care Research Center, 8700 Mason-Montgomery Rd, Mason, OH 45040, USA
| | - Patrick A. Limbach
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
| | - William R. Heineman
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221-0172, USA
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45
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Evenhuis CJ, Yang WC, Johns C, Macka M, Haddad PR. Fluorinated ethylenepropylene copolymer as a potential capillary material in CE. Electrophoresis 2007; 28:3477-84. [PMID: 17847133 DOI: 10.1002/elps.200700171] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In this work, a new generation UV-transparent polymer, fluorinated ethylenepropylene copolymer (FEP) exhibiting a low degree of crystallinity, extruded in dimensions similar to the most commonly used CE capillaries of approximately 80 mum id and about 360 mum od was investigated for its use as a CE capillary. FEP is transparent down to the low-UV region, and as fluorinated polymers in general are good electrical insulators and exhibit reasonable heat conductivity, it has considerable potential as a material for electrodriven analysis in capillary or microchip formats. The FEP capillary has been characterised with regard to some important aspects for its use as a CE capillary, including its profile of EOF versus pH, as well as procedures for manipulating EOF by coating the inner capillary wall with various semipermanent and dynamic layers. The FEP capillaries were tested and compared with fused-silica capillary for the separation of inorganic and small organic ions using conditions involving direct and indirect detection in the low-UV region. Finally, advantages of the use of the FEP capillary for simultaneous detection of a mixture containing nine inorganic cations and anions using indirect photometric detection with a movable light-emitting diode (LED) detector and a novel electrolyte are demonstrated.
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46
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Ji X, He Z, Pang D. On-line chemical generation of tris(2,2′-bipyridyl)ruthenium(III) and its application in CE with chemiluminescence detection. Electrophoresis 2007; 28:3260-7. [PMID: 17703469 DOI: 10.1002/elps.200700021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A novel tris(2,2'-bipyridyl)ruthenium(III) [Ru(bipy)(3) (3+)]-based chemiluminescence (CL) detection in CE using an on-line chemical generation scheme has been demonstrated. Two continuous streams respectively containing solutions of Ru(bipy)(3) (2+) and acidic cerium(IV) used as a homogeneous chemical oxidant are employed to generate Ru(bipy)(3) (3+), which is delivered into the reaction capillary of a coaxial flow interface and then reacted with analytes at the end of the separation capillary to yield light. The important operational parameters for separation and detection are identified and optimized. Four alpha-ketocarboxylic acids used as models, outside of the amine-containing compounds, are successfully separated and detected to evaluate the feasibility of the approach. The excellent resolution and detection sensitivity was achieved by using 50 mmol/L phosphate running buffer (pH 9.5) with 0.7 mmol/L CTAB, and CL reagent solution streams containing 0.15 mmol/L Ru(bipy)(3) (2+) and 0.8 mmol/L cerium(IV) (0.25 mol/L H(2)SO(4)), respectively. The concentration detection limits for alpha-ketocarboxylic acids were below 3.7x10(-8) mol/L (S/N = 3). The proposed method was applied to the determination of alpha-ketocarboxylic acids in five different honey samples with satisfactory results.
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Affiliation(s)
- Xinghu Ji
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, PR China
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47
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Diress AG, Lucy CA. Self-assembled coating for modification of the electro-osmotic flow in nonaqueous capillary electrophoresis using formamide. CAN J CHEM 2007. [DOI: 10.1139/v07-077] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The use of pure nonaqueous solvents in capillary electrophoresis (CE) can alter the separation selectivity and enhance the solubility of hydrophobic compounds and enables the use of higher voltages. However, control of the electro-osmotic flow (EOF) is essential. In this work, we report the use of self-assembled coatings for EOF modification and elimination of analyte adsorptions onto silica capillaries in pure formamide. Bilayer capillary coatings derived from the double chain cationic surfactant dimethyldioctadecylammonium bromide (2C18DAB) reverses the EOF in buffers such as acetate, formate, and phosphate. Reversed EOF of >1.1 × 10–4 cm2/Vs enables the separation of the pharmaceutical drugs propranolol, metoprolol, chloroquine, and chloropheniramine in less than 5 min with efficiencies of 0.2–0.5 million plates/m (66 000 to 165 000 plates). Chemical and physical factors affecting the coating stability and their influence on separation speed and efficiency of the cationic drugs in formamide are also investigated.Key words: capillary electrophoresis, cationic surfactants, electro-osmotic flow, formamide, nonaqueous solvents.
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48
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Liu Q, Li Y, Tang F, Ding L, Yao S. Cationic gemini surfactant as dynamic coating in CE for the control of EOF and wall adsorption. Electrophoresis 2007; 28:2275-82. [PMID: 17538923 DOI: 10.1002/elps.200600754] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The cationic gemini surfactant ethylene bis(1-dodecyldimethylammonium) dibromide was used as a dynamic coating to control EOF and prevent wall adsorption of basic proteins in CE for the first time. This gemini surfactant shows a more powerful capability in EOF reversal than traditional single-chained surfactant. The gemini surfactant reverses the EOF at a concentration level even less than 0.01 mM, and the EOF magnitude is affected by surfactant concentration, pH, ionic strength, and ions added in buffer. Highly efficient and rapid protein separation (N > 300,000) was obtained with buffer containing 2 mM gemini surfactant under pH ranging from 3 to 6. The effects of surfactant and buffer concentration on protein separation were investigated in detail. Under the optimal conditions, good repeatability (RSD of migration time <0.6% for run-to-run and <2.5% for day-to-day assays) and recovery (>90%) of tested proteins were obtained. This new dynamic coating is also suitable for biosample analysis.
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Affiliation(s)
- Qian Liu
- College of Chemistry and Chemical Engineering, Hunan University, Changsha, PR China
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49
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Diress AG, Yassine MM, Lucy CA. Semipermanent capillary coatings in mixed organic-water solvents for CE. Electrophoresis 2007; 28:1189-96. [PMID: 17366479 DOI: 10.1002/elps.200600440] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This report describes the creation of semipermanent capillary coatings that are compatible with organic-water solvent systems in CE. The coatings are created by simply rinsing the fused-silica capillary with long double-chain cationic surfactants, such as dimethyl-ditetradecyl ammonium bromide (2C(14)DAB), dihexadecyldimethyl ammonium bromide (2C(16)DAB), and dimethyldioctadecyl ammonium bromide (2C(18)DAB). These surfactants generate semipermanent bilayer coatings on the capillary surface, which display a high degree of stability in buffers containing up to 60% v/v of organic solvents, such as methanol and ACN. The coating stability increases with increasing hydrophobicity of the surfactant, i.e., with increasing chain length. For instance, the EOF changes by only 1.2% in a 2C(18)DAB-coated capillary after 130 capillary volumes of rinsing with 60% v/v methanol containing buffer. The bilayer coatings allow separations to be performed without the need to regenerate the coating between runs or to maintain the EOF modifier in the run buffer. Rapid separations (<2 min) of anions and basic drugs with migration time reproducibility of less than 0.5% RSD and efficiencies of 0.4-0.6 million plates/m are obtained. In addition, selectivity changes for small anions and cationic drugs are also observed when the organic solvent content is adjusted.
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Affiliation(s)
- Abebaw G Diress
- Department of Chemistry, Gunning/Lemieux Chemistry Centre, University of Alberta, Edmonton, Alberta, Canada
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Noblitt SD, Mazzoleni LR, Hering SV, Collett JL, Henry CS. Separation of common organic and inorganic anions in atmospheric aerosols using a piperazine buffer and capillary electrophoresis. J Chromatogr A 2007; 1154:400-6. [PMID: 17462662 DOI: 10.1016/j.chroma.2007.03.069] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Revised: 03/11/2007] [Accepted: 03/13/2007] [Indexed: 11/19/2022]
Abstract
The ability to monitor and quantify anionic components of aerosols is important for developing a better fundamental understanding of temporal and spatial variations in aerosol composition. Of the many methods that can be used to detect anions, capillary electrophoresis is among the most attractive ones because of its high separation efficiency, high resolving power for ionic compounds, and ability to be miniaturized for in-field monitoring. Here we present a method to baseline resolve common aerosol components nitrate, sulfate, chloride, and over two dozen organic acids in a single separation. A capillary electrophoresis separation utilizing a pH 5.78 piperazine buffer with 1,5-naphthalenedisulfonic acid as a probe for indirect UV absorbance detection was developed for this analysis. Previously, two different buffers were required to adequately separate all of these compounds. Electrophoretic mobilities, limits of detection, and migration time reproducibilities were measured for 38 organic and 8 inorganic anions. For solutions of low conductivity, detection limits for electrokinetic injections were found to be up to two orders of magnitude lower (0.2-0.4 microM) than those for pressure injection (1-45 microM). This separation was optimized and used for routine analysis of aqueous extracts of ambient atmospheric aerosols, but may be extended to other samples containing similar mixtures of anions.
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Affiliation(s)
- Scott D Noblitt
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
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