RESUMEN
Ethyl glucuronide (EtG), a metabolite of ethanol, is a marker of recent alcohol consumption. In the past few years, its analysis in body fluids has attracted considerable attention because it closes a gap between short time and long time alcohol markers such as ethanol and carbohydrate-deficient transferrin, respectively. The capillary zone electrophoresis (CZE) analysis of EtG in model mixtures and human serum is reported using uncoated and coated fused-silica capillaries together with acidic buffers in the pH range between 3.2 and 4.4 and indirect detection. In these approaches, separation of EtG from endogenous macro- and microcomponents (anionic serum components of high and low concentration, respectively) is based upon transient isotachophoretic stacking referred to as sample self-stacking. The selection of a favorable bufferco-ion and pH is shown to be crucial for optimized sensitivity. Abuffercomposed of 10 mM nicotinic acid and epsilon-aminocaproic acid (pH 4.3) is demonstrated to provide a detection limit for EtG in serum of 0.1 microg/ml, a value that is relevant for clinical and forensic purposes.
Asunto(s)
Electroforesis Capilar/métodos , Glucuronatos/sangre , Tampones (Química) , Electrólitos , Glucuronatos/aislamiento & purificación , Humanos , Concentración de Iones de Hidrógeno , Ácidos Mandélicos , Niacina , Sensibilidad y EspecificidadRESUMEN
It is a frequent phenomenon in practice that a sample contains bulk levels of more than one coionic component that affect the stacking behavior of minor analytes and in this way also the sensitivity of the method. Here, attention is paid to stacking resulting from the presence of a macrocomponent of leading type that is deteriorated by the presence of another macrocomponent of like charge in the sample. Based on the isotachophoretic model of migration in the initial period of separation, a theoretical approach was elaborated both for strong and weak electrolytes which describes the separation process and finds the conditions that define whether transient isotachophoretic stacking of the analyte takes place or not. It is shown that the crucial parameter is the ratio of the concentrations of macrocomponents migrating in front and behind the analyte of interest. The destacking effect can also be expected when the coion of the background electrolyte is present in the sample. Rules how to cope with effects of destackers present in the sample are given. Theoretical considerations are illustrated by computer simulations and verified experimentally. Examples of antagonistic effects of macrocomponents are demonstrated for model serum samples.
Asunto(s)
Electroforesis Capilar/métodos , Sensibilidad y EspecificidadRESUMEN
The behavior of two different fractions of the electrically conducting polymer polyaniline (PANI) was studied in order to characterize them using fast, simple, and cheap methods of capillary zone electrophoresis. In contradistinction to the expectations that the particles will bear a positive charge on their surface, in the milieu of electrolytes used for electrophoresis (0.01-0.05 M buffers of pH 4-8.5), the surface was demonstrated to be slightly negatively charged, which led to a slow migration to the anode. An evident charge was given to the particles after their interaction with micelles formed from surface active components, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS). An active electrophoretic migration and full separation of the PANI fractions was achieved by micellar electrokinetic chromatography (MEKC) with negatively charged SDS micelles. With this method, a reliable qualitative as well as quantitative analysis was performed in the concentration range of 0.1-1.6 mg/mL with a reproducibility of migration times better than 1.5%.
Asunto(s)
Compuestos de Anilina/análisis , Cromatografía Capilar Electrocinética Micelar/métodos , Electroforesis Capilar/métodos , Tamaño de la Partícula , Polímeros , SolucionesRESUMEN
The techniques of the on-line combination of capillary isotachophoresis with zone electrophoresis in two coupled capillaries (ITP-CZE) and a single capillary zone electrophoresis (CZE) were used for the sensitive determination of orotic acid (OA) in human urine. The simple CZE system was successfully applied for fast and reliable analyses of urine of healthy adult volunteers (the detection limit 1.7.10(-6) M OA, the total time of analysis 6 min). However, this method failed in analyses of OA in urine of ill children due to more complex matrix of the samples. Here, the ITP preconcentration and preseparation step coupled on-line with CZE proved to serve well with an electrolyte system developed and optimized for this purpose. The maximum selectivity and resolution of OA from other sample constituents in ITP-CZE was achieved by use of an electrolyte system of very low pH 2.15 both for ITP and CZE stage. The sensitivity of detection and simplicity of OA identification were enhanced by use of an external UV scanning detector. High sensitivity of ITP-CZE combination (limit of detection 3.10(-7) M OA), low sample consumption (1 microliter), good reproducibility of migration times (inter-day RSD < 1.86%) and acceptable reproducibility of the determination of OA in urine samples (average RSD = 7.27%) make this technique suitable for routine determination of trace concentration of OA especially in urine of ill children under various pathological conditions and medication.
Asunto(s)
Electroforesis Capilar/métodos , Electroforesis/métodos , Adulto , Niño , Cloruros/orina , Citratos/orina , Electrólitos , Humanos , Concentración de Iones de Hidrógeno , Lactatos/orina , Ácido Orótico/orina , Fosfatos/orina , Control de Calidad , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
This review evaluates the literature on continuous free flow electrophoresis, published during the last four years. Its aim is to serve not only experts in the field but also newcomers, and, therefore, it also briefly describes the principles of the method and the techniques used, referring to fundamental papers published earlier. The actual commercial instrumentation is briefly outlined. A substantial part of this review is devoted to the optimization of the performance of this method. Finally, diverse applications of fractionations of charged species in solution, ranging from small ions to biological particles and cells, are surveyed.
Asunto(s)
Electroforesis/instrumentación , Electroforesis/métodos , Animales , Células/química , Fenómenos Químicos , Química Física , Electroforesis/tendencias , Humanos , Membranas/química , Orgánulos/química , Proteínas/aislamiento & purificación , Reproducibilidad de los Resultados , Partículas Submitocóndricas/químicaRESUMEN
On-line combination of capillary isotachophoresis and zone electrophoresis performed in two coupled capillaries (ITP-CZE) is used for the trace analysis of L-ascorbic acid in human serum, urine and stomach fluid. At the ITP stage, anionic sample components are separated into individual zones and macrocomponents are detected and driven out of the migration path. In the CZE stage, only a small segment of the sample zones containing L-ascorbic acid is analyzed. High sensitivity of this hyphenated method (limit of detection, 0.09-0.15 mg/L), low sample volume consumption (2 microL), and acceptable reproducibility of the results (relative standard deviation, 8%) in the concentration range 0.1-15 mg/L demonstrate that the method is applicable for the study of the relation between the content of L-ascorbic acid in body fluids and the state of health of a person, in which lower amounts of L-ascorbic acid than the normal levels (i.e., 5.1-15.1 mg/L in human serum and 12.5-26.8 mg/L in urine) are expected. Possible interferences of other components of the body fluids are excluded by good correlation of the results obtained by the ITP-CZE method and a routine colorimetric method.
Asunto(s)
Ácido Ascórbico/análisis , Electroforesis Capilar/métodos , Líquidos Corporales/química , Colorimetría , Electrólitos , Electroforesis Capilar/normas , Humanos , SolucionesRESUMEN
The combination of capillary isotachophoresis and capillary zone electrophoresis may enhance greatly the performance of analytical capillary electrophoresis with respect to both separation power and the concentration sensitivity. The concentrating effects and the separation power of isotachophoresis allow the analysis of diluted samples and the elimination of interferences due to bulk components. The separation process of zone electrophoresis enables one to resolve the stack of trace analytes and detect the resulting individual zones with high sensitivity. The transition of isotachophoresis into zone electrophoresis plays the key role in the overall performance of this hyphenated technique. This article describes the dynamics of the conversion of isotachophoresis into zone electrophoretic mode and shows that the key role is played by the segments of the leading and terminating zones from the isotachophoretic stage. The magnitude of these segments directly effects the detection time as well as the separation width of the peaks of analytes. It is shown that these effects are also important in the analyses by capillary zone electrophoresis where isotachophoresis is induced by the sample itself. Finally, the paper presents a list of recommended, user-friendly, electrolyte systems which enable one to simply predict the performance of the combination isotachophoresis-zone electrophoresis.
Asunto(s)
Electroforesis Capilar/métodos , Electroforesis/métodos , ElectrólitosRESUMEN
Aracytidine (cytarabine, 1-beta-D-arabinofuranosylcytosine) is a synthetic analog of cytidine in which ribose is substituted by arabinose; it is used as a drug for the treatment of leukemia. A fast and reliable capillary electrophoretic method for the analysis of cytarabine and cytidine is described. The procedure utilizes the interactions with sodium dodecyl sulfate (SDS) micelles and borate, present in the background electrolyte, for the mobilization and selective separation of the analytes. The detection is carried out by UV absorbance at 275 nm. The method was applied both to pharmaceutical preparations and human serum. Analysis of an untreated serum requires 15 min; the detection limit is 0.8 microgram/mL and the relative standard deviation (RSD) is 5.3%.
Asunto(s)
Citarabina/aislamiento & purificación , Citidina/aislamiento & purificación , Electroforesis Capilar/métodos , Ácidos Bóricos , Citarabina/sangre , Citidina/sangre , Electrólitos , Humanos , Concentración de Iones de Hidrógeno , Micelas , Dodecil Sulfato de SodioRESUMEN
Capillary zone electrophoresis was optimized for the separation of thiouracil, methylthiouracil and propylthiouracil. Methylthiouracil could be determined in various types of urine (human, bovine, horse), either without any pretreatment or in ethyl acetate extracts, within 15 min. For identification, the simultaneous detection at three UV wavelengths (216, 245 and 278 nm) was advantageously used while for quantification the wavelength of the absorbance maximum at 278 nm was preferred. Under optimized conditions a linear response of the detector in the concentration range 0.1-100 ppm was obtained. On analysis of untreated urine, a detection limit of 0.5 ppm was found; for urine extracts the detection limit was 0.1 ppm. Univocal peak identification, based on absorption at three wavelength, was only possible above 2 ppm. Relative standard deviation for standard solutions of methylthiouracil, diluted in the background electrolyte, was 1%; for methylthiouracil in extracts dissolved in the background electrolyte it was 4.5%, and for methylthiouracil in untreated urine, 12.7%.
Asunto(s)
Antitiroideos/orina , Electroforesis Capilar/métodos , Metiltiouracilo/orina , Propiltiouracilo/orina , Tiouracilo/orina , Animales , Bovinos , Caballos , Humanos , Concentración de Iones de Hidrógeno , Metiltiouracilo/aislamiento & purificación , Propiltiouracilo/aislamiento & purificación , Tiouracilo/aislamiento & purificaciónAsunto(s)
Electroforesis Capilar/métodos , Electroforesis/métodos , Iones , Proteínas/aislamiento & purificación , Ácidos/análisis , Ácidos/aislamiento & purificación , Alcaloides/análisis , Alcaloides/aislamiento & purificación , Alopurinol/metabolismo , Naftalenosulfonatos de Anilina/análisis , Animales , Proteínas Sanguíneas/análisis , Proteínas Sanguíneas/aislamiento & purificación , Glucuronatos/análisis , Glucuronatos/aislamiento & purificación , Humanos , Concentración de Iones de Hidrógeno , Síndrome de Lesch-Nyhan/metabolismo , Muramidasa/aislamiento & purificación , Nucleótidos/análisis , Nucleótidos/aislamiento & purificación , Nucleótidos/orina , Fragmentos de Péptidos/análisis , Fragmentos de Péptidos/aislamiento & purificación , Fosfatos/análisis , Fosfatos/aislamiento & purificación , Hidrolasas Diéster Fosfóricas/análisis , Hidrolasas Diéster Fosfóricas/aislamiento & purificación , Tioglicolatos/análisis , Cloruro de Vinilo/metabolismoRESUMEN
Synthetic sulfated bis-lactobionic acid amides are important heparin-like pharmaceuticals. The synthesis of these compounds yields molecules differing in the number of sulfate groups, and, during the isolation procedure, the required species may partially decompose or take in some impurities. This article shows that capillary zone electrophoresis may serve well as an expedient method for the analysis of the above-mentioned pharmaceuticals. Complex-forming equilibria between the analytes and bivalent cations present in the background electrolyte bring selectivity necessary for the separation, and the detection at various wavelengths serves as an aid in the characterization of admixtures, decomposition products, and impurities. Capillary isotachophoresis may also be used for the analysis of these species, bringing about the potential of micropreparation of individual compounds and opening the chance for continuous free-flow electrophoresis.
Asunto(s)
Amidas/análisis , Anticoagulantes/análisis , Electroforesis Capilar , Electroforesis , Heparina/análogos & derivados , Ésteres del Ácido Sulfúrico/análisis , Disacáridos/análisis , Heparina/análisis , Estructura Molecular , Sistemas en LíneaRESUMEN
A new approach is described for highly sensitive chiral analyses by capillary zone electrophoresis, based on using an on-line combination of two capillaries filled with either chiral selective or achiral background electrolytes (BGE). Thus, the BGEs are selected in such a way that the first capillary provides optimum chiral selectivity and the second one optimum detection sensitivity. Direct chiral separations of enantiomers of mandelic, m-methoxymandelic, 3-phenyllactic and 3-indolelactic acids served as a model example for testing the approach proposed. The analyses were performed in a BGE containing acetate as a coion and L-OH-proline or aspartame as a chiral selector. For high sensitive analyses, an arrangement containing on-line combined chiral and achiral media were tested in one or two capillaries coupled via a bifurcation block. A detection limit as low as 10(-18) moles was reached in the column-coupling system when the direct chiral separation was performed in the first capillary, filled with 20 mM acetate buffer, pH 4.4, containing 8 mM Cu (II) and 16 mM aspartame (L-aspartyl-L-phenylalanine methylester) and separated enantiomers were detected in the second capillary, filled with 20 mM acetate buffer, pH 3.1. The principle described is of general use in cases where the separation and detection of analytes in question require mutually different BGEs to reach the optimum selectivity and sensitivity, respectively.
Asunto(s)
Electrólitos , Electroforesis Capilar/métodos , Estereoisomerismo , Aspartame/química , Cobre/química , Electroforesis Capilar/instrumentación , Indoles/química , Lactatos/química , Ácidos Mandélicos/química , Sensibilidad y EspecificidadRESUMEN
A method has been developed for the determination of the coccidiocidic drug halofuginone in feedstuff concentrates which is based on the combination of capillary isotachophoresis and capillary zone electrophoresis in the column-switching mode. The high load capacity of the isotachophoretic step and high sensitivity of the zone electrophoretic step enabled analysis of up to 25 microliters of sample solution containing as little as 10(-8) M halofuginone with excellent reproducibility (R.S.D. about 1%). Attention was paid to the possibility of the existence of transient local isotachophoresis in the zone electrophoretic step, and experimental and theoretical methods of revealing zones migrating isotachophoretically in the background electrolyte were shown.
Asunto(s)
Alimentación Animal/análisis , Coccidiostáticos/análisis , Electroforesis/métodos , Quinazolinas/análisis , Animales , Piperidinas , Aves de Corral , QuinazolinonasRESUMEN
A method is described for the determination of the triazine herbicides prometryne, desmetryne, terbutryne, OH-atrazine and OH-simazine in purified extracts of milk using analytical capillary isotachophoresis. The reproducibility of isotachophoretic analyses was 3.5% and the detection sensitivity reached 2 ng. Recovery of triazines from fortified samples of homogenized full milk (0.05 mg/L) was about 65%.
Asunto(s)
Electroforesis/métodos , Herbicidas/análisis , Leche/análisis , AnimalesRESUMEN
In the tops of corial papillae of the pig lip skin the authors sometimes observed besides typical sensory corpuscles also glomerular nerve endings. They are formed by one axon or they are polyaxon. The nerve fibres are richly branched in the formation. In electronogrammes a large number of axons is visible in cross sections round some of which there are more or less formed lamellous systems up to four lamellae. Between the axons there are nuclei of Schwann cells, on the surface there is a thin capsule of fibrocyte character. In non-primate mammals the typical receptor in the corium of the skin are simple corpuscles, in primates glomerular nerve endings. As concerns sensory corpuscles it is the other way round. The authors are of the opinion that the observed glomerular endings represent morphologically a transitory formation. With respect to the occurrence of lamellous complexes in the glomeruli, they can be considered as equivalent to simple sensory corpuscles with rapid adaptation.