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1.
J Chromatogr A ; 920(1-2): 367-75, 2001 Jun 22.
Artículo en Inglés | MEDLINE | ID: mdl-11453022

RESUMEN

A macroporous, spherical, 7 microm, polystyrene-divinylbenzene (PS-DVB), reversed-phase adsorbent (PRP-1) was evaluated as a stationary phase for the capillary electrochromatographic (CEC) separation of neutral, acidic, and basic analytes of pharmaceutical interest. Electroosmotic flow (EOF) for a PRP-1 packed capillary is nearly constant over the pH 2 to 10 range and is higher than for a silica-based C18 packed capillary on the acidic side. EOF increases with an increase in buffer acetonitrile concentration or as applied potential increases. As analyte hydrophobicity increases, analyte retention and migration time increases. Increasing buffer acetonitrile concentration reduces analyte partitioning with the PS-DVB stationary phase and analyte retention and migration time decreases. When exchange sites are present on the PS-DVB copolymer, EOF (EOF is reversed for the anion-exchanger) increases as the exchange capacity increases. An increased exchange capacity also reduces partitioning of the analyte with the PS-DVB matrix and analyte retention and migration time decrease. Because of excellent stability in an acid environment, the PRP-1 packed capillary can be used in strong acid buffer solution and weak acid and base analytes depending on pKa values can be separated as neutral species and cations, respectively. CEC separations on a PRP-1 capillary of neutral steroids, weak base pharmaceuticals (separation as cations), purines and pyrimidines (as cations), fatty acids (as undissociated species), and sulfa derivatives (as cations) are described. Efficiency for the PRP-1 packed capillary for acetone or thiourea as the analyte is about 6 x 10(4) plates m(-1).


Asunto(s)
Cromatografía Capilar Electrocinética Micelar/métodos , Resinas de Intercambio Iónico , Polímeros , Ácidos Grasos/aislamiento & purificación , Preparaciones Farmacéuticas/aislamiento & purificación , Purinas/aislamiento & purificación , Pirimidinas/aislamiento & purificación , Esteroides/aislamiento & purificación , Sulfanilamidas/aislamiento & purificación
2.
J Chromatogr A ; 884(1-2): 297-309, 2000 Jul 07.
Artículo en Inglés | MEDLINE | ID: mdl-10917448

RESUMEN

A fused-silica capillary that is wall-modified via chemically bonding a sulfonated polymer to the capillary wall has a uniform negative charge density on its surface and produces an electroosmotic flow (EOF) greater than 4 x 10(-4) cm2 V(-1) s(-1) The EOF is nearly independent of buffer pH over the pH range of 2 to 10 and is lower than the EOF obtained for the bare fused-silica capillary at the more basic pH but is higher at the more acidic buffer pH. Optimization of buffer pH can be based on analyte pKa values to improve the overall quality of the capillary zone electrophoresis (CZE) separation of complex mixtures of weak acid and base analytes. Because of the high EOF in an acidic buffer, the capillary is useful for the separation of weak organic bases which are in their cation forms in the acidic buffer. EOF for the sulfonic acid bonded phase capillary can be adjusted via buffer additives such as organic solvent, tetraalkylammonium salts, multivalent cations and alkylsulfonic acids. The advantages of utilizing buffer pH and the EOF buffer modifiers to enhance migration time, selectivity, and resolution in CZE separations with this capillary are illustrated using a series of test analyte mixtures of inorganic anions, carboxylic acids, alkylsulfonic acids, benzenesulfonic acids, sulfas, pyridines, anilines or small-chain peptides.


Asunto(s)
Electroforesis Capilar/métodos , Ácidos Alcanesulfónicos/química , Tampones (Química) , Concentración de Iones de Hidrógeno , Polímeros/química
3.
Anal Chem ; 72(24): 5930-8, 2000 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-11140759

RESUMEN

Macroporous poly(styrene-divinylbenzene) (PSDVB), PRP-1, a reversed-phase adsorbent, and PSDVB-based strong acid cation exchangers and strong base and weak base anion exchangers were evaluated as stationary phases for capillary electrochromatography (CEC). Electroosmotic flow (EOF) for adsorbent and exchanger packed fused-silica capillaries for acetone as the marker increases with increasing ion exchange capacity, buffer organic solvent concentration, and applied voltage, is nearly independent of pH, and decreases with increased buffer ionic strength. For anion exchangers, EOF is reversed. Thiourea, acetone, acrylamide, nitromethane, propanal, and acetic acid were evaluated as EOF markers and undergo weak interaction with the PSDVB-based stationary phases. EOF in a basic buffer is greater than or equal to silica-based C-18 and cation exchanger packed capillaries. For an acidic buffer, EOF for a PRP-1 capillary is almost twice the C-18 packed capillary. As analyte hydrophobicity increases, retention and migration time increases for the PSDVB-based stationary phases. As exchange capacity increases, availability of the polymeric matrix for analyte partitioning decreases, causing analyte migration time to decrease. Increasing buffer organic solvent concentration decreases analyte retention. The PSDVB-based stationary phases provide good resolving power and reproducibility and are applicable to the CEC separation of neutral, weakly acidic, and basic analytes. Efficiency, however, is less than obtained with silica-based stationary phases. Because of stability in a strong acid buffer, the CEC separation of weak acids, where dissociation is suppressed, and weak bases as cations is possible. Separations of short-chain alkyl aldehydes, methyl ketones, aromatic hydrocarbons, substituted benzene derivatives, and short-chain carboxylic acids are described.

4.
In Vitro Cell Dev Biol Anim ; 35(7): 383-8, 1999.
Artículo en Inglés | MEDLINE | ID: mdl-10462201

RESUMEN

Difluoromethylidene bisphosphonate (F2MBP) is one of the many bisphosphonates known to inhibit bone resorption in vitro and in vivo. We have developed an analytical method, employing anion exchange and postcolumn indirect fluorescence detection, by which F2MBP can be quantified in bone samples. The objective of this study was to relate the concentration of F2MBP in embryonic bones treated in organ culture to the physiological effects of the compound, such as bone resorption (i.e., the amount of 45Ca released into the medium from prelabeled bones) and viability of the osteoclast population (i.e., the incidence of abnormal osteoclasts). Osteoclasts in bones treated with F2MBP exhibited morphological features of apoptosis, such as nuclear fragmentation. Both the number and percentage of these abnormal cells increased with dose of F2MBP and duration of incubation. The decrease in normal osteoclasts was correlated with the decreased amount of 45Ca released into the medium. Bones treated with F2MBP for only the first 5 min of the 48-h incubation period had similar numbers of abnormal osteoclasts and amounts of 45Ca released, as had bones incubated with F2MBP continuously for 48 h. The uptake of F2MBP into the bone was rapid. Bones treated with F2MBP for 6 h were similar to bones treated with F2MBP for the entire 48-h incubation period, both in F2MBP concentration and the 45Ca release ratios. These relationships between concentrations of F2MBP within bone and osteoclast activity and viability implicate apoptosis in the mechanism by which this bisphosphonate inhibits bone resorption.


Asunto(s)
Huesos/química , Difosfonatos/análisis , Osteoclastos/química , Animales , Huesos/citología , Huesos/embriología , Femenino , Técnicas de Cultivo de Órganos , Ratas , Ratas Sprague-Dawley
5.
J Chromatogr A ; 850(1-2): 143-52, 1999 Jul 30.
Artículo en Inglés | MEDLINE | ID: mdl-10457475

RESUMEN

Bisphosphonic acids and their salts can be detected after their liquid chromatographic separation by post-column indirect fluorescence detection (IFD). After separation the analyte is combined with the highly fluorescent Al(3+)-morin (2',3,4',5,7-pentahydroxyflavone) solution and fluorescence decreases because of the formation of the nonfluorescent Al(3+)-bisphosphonate complex. The decrease in fluorescence is proportional to the amount of bisphosphonate present. Separation of the multivalent anionic bisphosphonate analytes from other anions and sample matrix is achieved on a strong base anion-exchange column with a strong, basic eluent. The post-column reaction variables, which influence IFD, are identified and optimized for the detection of the bisphosphonates after separation on the anion exchanger. The method is selective, since only a few anions will undergo a reaction with the Al(3+)-morin solution, and sensitive, detection limit for difluoromethylene bisphosphonate, F2MDP, is 4 ng for S/N = 3. The separation-IFD method can be applied to the determination of bisphosphonates, such as F2MDP, ethane-1-hydroxy-1,1-bisphosphonic acid, dichloromethylene bisphosphonic acid, 4-amino-1-hydroxybutane-1,1-bisphosphonic acid, in biological samples. The separation-IFD method is also applicable to the detection of inositol phosphate anions.


Asunto(s)
Cromatografía por Intercambio Iónico/métodos , Difosfonatos/análisis , Espectrometría de Fluorescencia
6.
J Chromatogr ; 602(1-2): 197-204, 1992 Jun 05.
Artículo en Inglés | MEDLINE | ID: mdl-1400853

RESUMEN

Glyphosate [N-(phosphonomethyl)glycine] and its metabolite aminomethylphosphonic acid (AMPA) were separated and detected by a postcolumn indirect detection strategy. Separation can be done on a cation-exchange column, where glyphosate elutes before AMPA, or on an anion-exchange column, where the elution order is reversed. Detection was achieved by using a fluorescent Al(3+)-morin postcolumn reagent. When the postcolumn reagent combines with the column effluent in a mixing tee, the fluorescence decreases in the presence of both analytes. Variables affecting the postcolumn indirect fluorescence detection were established and optimized; the major factors were postcolumn pH and volume and temperature of the postcolumn reaction coil. Detection limits, defined as three times the background noise, for glyphosate and AMPA separated on an anion-exchange column were 14 and 40 ng, respectively.


Asunto(s)
Glicina/análogos & derivados , Herbicidas/análisis , Cromatografía por Intercambio Iónico , Glicina/análisis , Compuestos Organofosforados/análisis , Espectrometría de Fluorescencia , Glifosato
7.
Anal Chem ; 64(9): 1003-8, 1992 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-1590583

RESUMEN

The retention of alkanesulfonate and alkyl sulfate surfactants, which was determined on a reversed stationary phase as a function of mobile-phase ionic strength, is consistent with a double-layer type interaction at the stationary-phase surface. Increasing the mobile-phase ionic strength not only increases retention but also improves resolution because peak widths are significantly reduced. The type of cation provided by the ionic strength salt also enhances retention, reduces peak width, and improves resolution. Lithium hydroxide is an ideal electrolyte for the separation of multicomponent mixtures of alkanesulfonate and alkyl sulfate surfactants. When the column effluent is passed through a postcolumn anion micromembrane suppressor, the conductivity due to the electrolyte is minimized and conductivity detection is sensitive, yielding a detection limit of about 0.3 nmol of injected analyte for a 3:1 signal:noise ratio. Multicomponent alkanesulfonate and alkyl sulfate mixtures from C2 to C18 are baseline resolved by using a mobile-phase gradient whereby CH3CN concentration increases and LiOH concentration decreases.


Asunto(s)
Ácidos Sulfónicos/aislamiento & purificación , Ácidos Sulfúricos/aislamiento & purificación , Tensoactivos/aislamiento & purificación , Cromatografía Liquida , Concentración Osmolar
8.
J Chromatogr ; 509(2): 357-68, 1990 Jun 22.
Artículo en Inglés | MEDLINE | ID: mdl-2211900

RESUMEN

Ruthenium(II) 1,10-phenanthroline, Ru(phen)3(2+), and ruthenium(II) 2,2'-bipyridyl, Ru(bipy)3(2+), salts were evaluated as mobile phase additives for the liquid chromatographic separation of small-chain peptides on a polystyrene-divinylbenzene copolymeric (Hamilton PRP-1) stationary phase. In a basic mobile phase peptides are anions, and retention, resolution and detection occur because of the interactions between the stationary phase, the RuII complex and the peptide anion. Since the RuII complex concentration changes in the analyte band relative to the background eluent RuII complex concentration, the peptide can be detected by indirect photometric detection using the wavelength where the RuII complex absorbs. Peptide analyte peaks may be positive or negative depending on the counter-anion and its concentration. Small-chain peptides that do not contain chromophoric side-chains are detected without derivatization at about 0.1 nmol injected at a 3:1 signal-to-noise ratio. Factors that affect retention, resolution and indirect photometric detection are the RuII complex, its mobile phase concentration, mobile phase pH and solvent composition, and the type and concentration of the mobile phase counter-anion and/or buffer anion.


Asunto(s)
Cromatografía Liquida/métodos , Péptidos/análisis , 2,2'-Dipiridil/análogos & derivados , Complejos de Coordinación , Compuestos Organometálicos , Fenantrolinas , Poliestirenos
9.
J Chromatogr Sci ; 27(8): 485-90, 1989 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-2547806

RESUMEN

Iron(II) 1,10-phenanthroline, Fe(phen)3(2+), salts are used as mobile phase additives for the liquid chromatographic separation of alkyl sulfonates and sulfates on the reversed-phase PRP-1. As alkyl chain length increases retention increases. For a given chain length an alkyl sulfate is more retained than the corresponding alkyl sulfonate. Major elution variables that affect retention are mobile phase solvent and counteranion concentration. Indirect photometric detection is used to detect alkyl sulfonates and sulfates at 510 nm where Fe(phen)3(2+) salts absorb. Conditions for isocratic and gradient elution of multicomponent mixtures are described. Detection limits depending on analyte approached 0.1 nmol for isocratic elution and 3 nmol for gradient elution.


Asunto(s)
Alcanosulfonatos/aislamiento & purificación , Cromatografía Líquida de Alta Presión/métodos , Análisis Espectral/métodos , Sulfatos/aislamiento & purificación
10.
J Chromatogr ; 466: 291-300, 1989 Apr 19.
Artículo en Inglés | MEDLINE | ID: mdl-2545737

RESUMEN

Mixed bed ion-exchange (MBIE) columns containing alumina and silica were evaluated for the simultaneous separation of anion and cation analytes. At the mobile phase pH used alumina provides anion exchange sites while silica provides cation exchange sites. Since alumina and silica exhibit weak acid and base properties, their anion and/or cation exchange properties are pH dependent. Ion exchange capacities, rates of exchange and analyte ion exchange selectivities are also pH dependent. The major mobile phase parameters affecting analyte anion and cation resolution and elution order are pH and type and concentration of counter anion and counter cation, respectively. The weight ratio of the two exchangers and/or the exchange capacities of the two in the column can also be used to alter resolution and elution order. Several examples of the simultaneous separation of inorganic mono- and divalent anions and cations using a single sample injection, a single column and a single detector (conductivity) illustrate the parameters and scope of the alumina-silica MBIE column.


Asunto(s)
Aniones/aislamiento & purificación , Cationes/aislamiento & purificación , Óxido de Aluminio , Cromatografía por Intercambio Iónico , Concentración de Iones de Hidrógeno , Indicadores y Reactivos , Concentración Osmolar , Dióxido de Silicio
20.
Anal Chem ; 44(4): 671-5, 1972 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-22309521
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