Flow-gating interface
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A coaxial flow-gating interface is described in which the separation capillary passes through the sampling capillary. Continuous flow of the sample solution flowing out of the sampling capillary is directed away from the injection end of the separation capillary by counter-current flow of the gating solution. During the injection, the flow of the gating solution is interrupted, so that a plug of solution is formed at the inlet into the separation capillary, from which the sample is hydrodynamically injected. Flow-gating interfaces are originally designed for on-line connection of capillary electrophoresis with analytical flow-through methods. The basic properties of the described coaxial flow-gating interface were obtained in a simplified arrangement in which a syringe pump with sample solution has substituted analytical flow-through method. Under the optimized conditions, the properties of the tested interface were determined by separation of K+ , Ba2+ , Na+ , Mg2+ and Li+ ions in aqueous solution at equimolar concentrations of 50 μM. The repeatability of the migration times and peak areas evaluated for K+ , Ba2+ and Li+ ions and expressed as relative standard deviation did not exceed 1.4%. The interface was used to determine lithium in mineral water and taurine in an energy drink.
- MeSH
- elektroforéza kapilární * MeSH
- energetické nápoje analýza MeSH
- ionty analýza MeSH
- lithium analýza MeSH
- minerální vody analýza MeSH
- Publikační typ
- časopisecké články MeSH
A new kind of flow gating interface (FGI) has been designed for online connection of CE with flow-through analytical techniques. The sample is injected into the separation capillary from a space from which the BGE was forced out by compressed air. A drop of sample solution with a volume of 75 nL is formed between the outlet of the delivery capillary supplying the solution from the flow-through apparatus and the entrance to the CE capillary; the sample is hydrodynamically injected into the CE capillary from this drop. The sample is not mixed with the surrounding BGE solution during injection. The functioning of the proposed FGI is fully automated and the individual steps of the injection process are controlled by a computer. The injection sequence lasts several seconds and thus permits performance of rapid sequential analyses of the collected sample. FGI was tested for the separation of equimolar 50 μM mixture of the inorganic cations K+ , Ba2+ , Na+ , Mg2+ , and Li+ in 50 mM acetic acid/20 mM Tris (pH 4.5) as BGE. The obtained RSD values for the migration times varied in the range 0.7-1.0% and the values for the peak area were 0.7-1.4%; RSD were determined for ten repeated measurements.
An electrophoretic apparatus with a flow-gating interface has been developed, enabling hydrodynamic sequence injection of the sample into the separation capillary from the liquid flow by underpressure generated in the outlet electrophoretic vessel. The properties of the apparatus were tested on an artificial sample of an equimolar mixture of 100μM potassium and sodium ions and arginine. The repeatability of the injection of the tested ions expressed as RSD (in%) for the peak area, peak height and migration time was in the range 0.76-2.08, 0.18-0.68 and 0.28-0.48, respectively. Under optimum conditions, the apparatus was used for sequence monitoring of the reaction between the antidiabetic drug phenyl biguanide and the glycation agent methyl glyoxal. The reaction solution was continuously sampled by a microdialysis probe from a thermostated external vessel using a syringe pump at a flow rate of 3μLmin(-1) and was injected into a separation capillary at certain time intervals. The electrophoretic separation progressed in a capillary with an internal diameter of 50μm with a length of 11.5cm and was monitored using a contactless conductivity detector.
For connecting flow-through analytical methods with capillary electrophoresis, a chip working in the air-assisted flow gating interface regime is cast from poly(dimethylsiloxane). In the injection space, the exit from the delivery capillary is placed close to the entrance to the separation capillary. Prior to injecting the sample into the separation capillary, the background electrolyte is forced out of the injection space by a stream of air. In the empty space, a drop of the sample with a volume of <100 nL is formed between the exit from the delivery capillary and the entrance into the separation capillary, from which the sample is injected hydrodynamically into the separation capillary. After injection, the injection space is filled with BGE, and the separation can be begun. Three geometric variants for the mutual geometric arrangement of the delivery and separation capillaries were tested: the delivery capillary is placed perpendicular to the separation capillary, from either above or below, or the capillaries are placed axially, that is, directly opposite one another. All of the variants are equivalent from the analytical and separation efficiency viewpoints. The repeatability expressed by RSD is up to 5%. The tested flow gating interface variants are also suitable for continuous and discontinuous sampling at flow rates of the order of units of μL/min. The developed instrument for sequential electrophoretic analysis operates fully automatically and is suitable for rapid sequential monitoring of dynamic processes.
- MeSH
- elektroforéza kapilární * MeSH
- elektrolyty MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
An analytical apparatus is described, based on on-line connection of electrophoresis in a short capillary with a dialysis unit enabling dialysis in micro-litre sample volumes into submicro-litre volumes of an acceptor solution in a dialysing fibre. After a defined dialysis time, the dialysate from the dialysing fibre is injected into a separation capillary through an air-assisted flow-gating interface cast from PDMS. In the flow-gating injection space, the exit from the delivery capillary bringing the dialysate is placed directly opposite the entrance into the separation capillary at a distance of 380 μm. In order to enable injection of a very small volume of dialysate, the background electrolyte is forced out of the injection space with air before the injection, so that a drop of dialysate with a volume of about 0.1 μL is formed between the exit from the delivery and the entrance into the separation capillary; the dialysate is injected hydrodynamically from this dialysate drop. Then the injection space is filled with the background electrolyte and the separation is commenced. The basic properties of the apparatus were tested on model mixtures of inorganic cations (K+, Ba2+ and Na+) and organic molecules (creatinine, histidine and arginine). The applicability to real samples was tested on the determination of basic amino acids (histidine, lysine and arginine) in a blood serum sample.
- Publikační typ
- časopisecké články MeSH
A miniature probe for electromembrane extraction is developed and constructed. The tubular probe with an internal volume of 1.1 μL is made of polypropylene hollow fiber with a supported liquid membrane of 85% nitrophenyloctyl ether (NPOE) with 15% bis(2-ethylhexyl)phosphonic acid (DEHP). The probe is connected on-line to the electrophoresis with short separation capillary via an air assisted flow gating interface cast from poly (dimethylsiloxane). The compact instrument is computer controlled via LabView. The probe parameters are tested for extraction of creatinine and basic amino acids from artificial solution and human urine. The sensitivity of the electrophoretic determination after 300 s extraction at 150 V compared to the sensitivity without extraction is 4.9-fold and 2.6-fold higher for creatinine and arginine, respectively. The RSDs for peak area measured from 5 repeated extractions of 50 μM solutions are 7.5%, 7.2%, 8.6% and 9.2% for Crea, Lys, Arg and His, respectively. The probe can be used for all-day measurements. The preparation of the probe is simple and requires no special tool.
The review presents an evaluation of the development of on-line, at-line and in-line sample treatment coupled with capillary and microchip electrophoresis over the last 10 years. In the first part, it describes different types of flow-gating interfaces (FGI) such as cross-FGI, coaxial-FGI, sheet-flow-FGI, and air-assisted-FGI and their fabrication using molding into polydimethylsiloxane and commercially available fittings. The second part deals with the coupling of capillary and microchip electrophoresis with microdialysis, solid-phase, liquid-phase, and membrane based extraction techniques. It mainly focuses on modern techniques such as extraction across supported liquid membrane, electroextraction, single drop microextraction, head space microextraction, and microdialysis with high spatial and temporal resolution. Finally, the design of sequential electrophoretic analysers and fabrication of SPE microcartridges with monolithic and molecularly imprinted polymeric sorbents are discussed. Applications include the monitoring of metabolites, neurotransmitters, peptides and proteins in body fluids and tissues to study processes in living organisms, as well as the monitoring of nutrients, minerals and waste compounds in food, natural and wastewater.
- MeSH
- elektroforéza kapilární metody MeSH
- elektroforéza mikročipová * metody MeSH
- mikrodialýza MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
We have developed an improved technique for fast cooling and heating of solutions superfusing isolated cells under patch-clamp or calcium imaging conditions. The system meets the requirements for studying temperature dependency of all kinds of ion channels, in particular temperature-gated ion channels. It allows the application of temperature changes within a range of 5-60 degrees C at maximum rates of -40 degrees C/s to 60 degrees C/s. Barrels filled with different solutions are connected to a manifold consisting of seven silica capillaries (320 microm inner diameter, i.d.). A common outlet consists of a glass capillary through which the solutions are applied onto the cell surface. The upper part of this capillary is embedded in a temperature exchanger driven by a miniature Peltier device which preconditions the temperature of the passing solution. The lower part of the capillary carries an insulated copper wire, densely coiled over a length of 7 mm, and connected to a dc current source for resistive heating. The Peltier device and the heating element are electrically connected to the headstage probe which is fixed on to a micromanipulator for positioning of the manifold. The temperature of the flowing solution is measured by a miniature thermocouple inserted into the common outlet capillary near to its orifice which is placed at a distance of less than 100 microm from the surface of the examined cell. The temperature is either manually controlled by voltage commands or adjusted via the digital-to-analog converter of a conventional data acquisition interface. Examples are given of using the device in patch-clamp studies on heterologously expressed TRPV1, TRPM8, and on cultured rat sensory neurons.
- MeSH
- akční potenciály fyziologie MeSH
- analýza selhání vybavení MeSH
- buněčné kultury metody přístrojové vybavení MeSH
- design vybavení MeSH
- financování organizované MeSH
- kultivované buňky MeSH
- lidé MeSH
- membránové potenciály fyziologie MeSH
- metoda terčíkového zámku metody přístrojové vybavení MeSH
- neurony aferentní fyziologie MeSH
- nízká teplota MeSH
- perfuze přístrojové vybavení MeSH
- prostředí kontrolované MeSH
- vysoká teplota MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- hodnotící studie MeSH
... Directing Their Own Synthesis 4 -- Self-replicating Molecules Undergo Natural Selection 6 -- Information Flows ... ... Actively Swept to One Pole of the Cell in the Process of “Capping” -- Conflicting Views on How Cells Cap: Flow ... ... Translocation” and Can Involve Water-soluble Binding Proteins -- Some Transmembrane Protein Channels Are “Gated ... ... Electron Transport from ATP Synthesis 508 -- Respiratory Control Normally Restrains the Electron -- Flow ... ... Photoreceptor Cells of the Retina -- Summary -- Renewal by Simple Duplication -- The Liver Is an Interface ...
xxxix, 1146 s. : il., tab. ; 28 cm
- MeSH
- biologie buňky MeSH
- molekulární biologie MeSH
- Publikační typ
- monografie MeSH
- Konspekt
- Biochemie. Molekulární biologie. Biofyzika
- NLK Obory
- biologie
- cytologie, klinická cytologie
