Thermal effects and band spreading in capillary electro-separation

Knox, John H.

doi:10.1007/bf02268176

Cited by 319 publications

(178 citation statements)

References 14 publications

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“…As in HPLC, the column contains a stationary phase. However, flow in CEC is generated electroosmotically, as in CE, and hence the flow profile is plug-like [26]. This allows for lower reduced plate heights and consequently higher efficiencies compared to HPLC.…”

Section: Introductionmentioning

confidence: 99%

Size‐exclusion capillary electrochromatographic separation of polysaccharides using polymeric stationary phases

2003

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We report the successful size-based separations of large, neutral polysaccharides using capillary electrochromatography (CEC). As the polysaccharides possessed little chromophore for photometric detection, two separate approaches were taken. In the first approach, indirect detection was combined with size-exclusion chromatography using a sulfonated polystyrene/divinylbenzene stationary phase. The separations were performed using a 300 Å pore size stationary phase under aqueous conditions. Nonsize based interactions were minimal using this material, resulting in an effective calibration range of molecular masses 180 to 112 000 g?mol 21 for pullulans. In the second approach, the polysaccharides were derivatized with phenylisocyanate and were subsequently separated on columns made using a combination of high capacity ionexchanger and a neutral polystyrene/divinylbenzene material of various pore sizes. The sulfonated ion-exchange phase provided the electroosmotic flow, while the mixed pore size material provided the extended calibration range. The linear range for this primarily nonaqueous system using tetrahydrofuran was determined to be from molecular masses 738 to 404 000 g?mol 21 of the original, untagged pullulan. This approach overcame the limited solubility issue associated with analysis of some polysaccharides. Analysis of pullulan and amylose samples by CEC correlated well with results obtained by conventional high-performance liquid chromatography (HPLC). The sizeexclusion electrochromatographic separations provide an alternative mode for determining the relative molecular weights of polysaccharides with reduced sample and solvent consumption, as well as analysis times.

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Section: Introductionmentioning

confidence: 99%

Size‐exclusion capillary electrochromatographic separation of polysaccharides using polymeric stationary phases

2003

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“…What is gained in c .... i by higher buffer concentrations, is lost as a result of the smaller admissible d c values. We note that Knox [16] reached quite another conclusion, which we believe is due to an incorrect assessment of the production rate.…”

Section: Choice Of Buffer Concentration C Omentioning

confidence: 83%

“…As treated in some detail by Knox and Grant [18] and Grushka et al [19], rto t is built up of three main contributions, corresponding to the heat transfer resistance of the lumen, the wall and the surrounding thermostatting medium: rtot = rlu m + rwalt + rth m (22) As shown by many workers [16,17,19], rlu m and rwa u can be easily predicted:…”

Section: Case I Average Temperature Elevation Limited Tomentioning

confidence: 99%

Optimum conditions for preparative operation of capillary zone electrophoresis

Cifuentes

Kok

et al. 1995

Journal of Chromatography A

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Optimum conditions for preparative operation of capillary zone electrophoresisCifuentes, A.; Xu, X.; Kok, W.T.; Poppe, H. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. AbstractThe possibilities to use capillary zone electrophoresis (CZE) as a preparative tool have been studied, mostly from a theoretical point of view. The preparative performance of CZE is quantitated by the production rate, the amount of analyte that can be purified per unit of time. The production rate available with CZE is shown to depend in the first place on the chemical characteristics of the analyte-buffer combination. A figure of merit can be defined for a buffer system, describing its susceptibility to analyte overloading. Methods to find an optimal bufer system are referred to. It is shown that the loadability of the system is inversely proportional to the plate number required for the separation.A second important factor for the maximum production rate is shown to be the thermal management of the instrumental system. The average increase of the solution temperature and the non-uniform migration velocity by temperature differences within the solutions are discussed. It is shown that in practical cases the temperature rise of the solutions will be the main limiting factor when high fields are used. With low fields, which in general give a higher production rate, siphoning of the solution becomes the dominant limitation for the production rate.With cylindrical capillaries the highest production rate that can be obtained under practical conditions is in the order of 5.10 -13 mol s -1. Experimental and theoretical results indicate that with rectangular capillaries the production rate can be increased by a factor of three.

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Section: High Salt Capillary Electrophoresismentioning

confidence: 99%

“…The temperature gradients can cause natural convection, which will remix separated sample zones, distort the peak shapes, and damage the separation performance. There are several papers that devote to discussing the temperature profile inside the capillary, the thermal effects, and the zone spreading [146][147][148].However, using a lower salt concentration in the sample than in the electrolyte to achieve electrostacking effect is used in many cases to improve separation efficiency and detectability. In a stody by Chien and Burghi [149], an enhancement factor ~ 100 was achieve for the sample injection using electrostacking method.…”

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confidence: 99%

Capillary electrophoresis separation of neutral organic compounds, pharmaceutical drugs, proteins and peptides, enantiomers and anions

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This manuscript has been reproduced from the microfilm master. UMI films the t»ct directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer.The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction.In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion.Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one e7q)osure and is included in reduced form at the back of the book.Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. The effect of adding this new surfactant to the acidic electrolyte was also investigated. UMIWorking at acidic condition at pH 2.4 has the advantage that electroosmotic flow is virtually eliminated. Neutral compounds are dragged by their association with the surfactant, moving as the same direction as the surfactant, resulting in fast separations. Basic compounds are also investigated under the same conditions. Excellent resolution of a mixture of 19 polyaromatic hydrocarbons was obtained in only 20 min.Incorporation of cetyltrimethylammonium bromide in the electrolyte is shown to dynamically coat the capillary and reverse electroosmotic flow. The coating prevents basic proteins and peptides adsorption into the capillary wall, resulting in high separation efficiencies. A systematic study of experimental parameters demonstrated the importance of selecting a suitable buffer and an appropriate pH.Gliral recogmtion mechanism is smdied using several novel synthetic surfactants as chiral selectors, which are made from amino acids reacting with al&yl chloroformates. It was found that enantiomeric resolution can be readily manipulated by varying the alkyl groups (different chain lengths), amino acids and surfactant concentrations. Sulfonated Bcyclodextrin is also employed as a chiral selector to compare chiral selectivity with these synthetic surfactants. A duo-chiral selectors system is further investigated for the possibility of eliminating some tedious steps in chiral compounds method development.A satisfactory separation of both inorganic and organic anions is obtained using electrolyte solutions as high as 5 M sodium chloride using direct photometric detection. The temperature inside the capillary that ...

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Thermal effects and band spreading in capillary electro-separation

Cited by 319 publications

References 14 publications

Size‐exclusion capillary electrochromatographic separation of polysaccharides using polymeric stationary phases

Size‐exclusion capillary electrochromatographic separation of polysaccharides using polymeric stationary phases

Optimum conditions for preparative operation of capillary zone electrophoresis

Capillary electrophoresis separation of neutral organic compounds, pharmaceutical drugs, proteins and peptides, enantiomers and anions

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