Capillary electrophoresis is an analytical technique that separates ions based on their electrophoretic mobility with the use of an applied voltage. Thepercentagecontentofone or more components of the substance to be examined is calculatedbydeterminingtheareaofthepeakorpeaksas a percentage of the total area of all the peaks, excluding those due to solvents or any added reagents and those below the disregard limit. Capillary zone electrophoresis an overview sciencedirect. Effect of joule heating on electrokinetic transport cetin. The joule heating jh is a ubiquitous phenomenon in electrokinetic flow due to the presence of electrical potential gradient and electrical current. Thermal effect on microchannel electroosmotic flow with. Electromigration dispersion in a capillary in the presence of. It supplements the electrophoretic motion of ions in capillary electrophoresis. Dec 03, 2015 types of electrophoresis gel electrophoresis high resolution electrophoresis capillary electrophoresis isoelectric focussing immunochemical pulsed field 2d electrophoresis cellulose acetate electrophoresis at alkaline ph 8. Endeavors in capillary electrophoresis ce began as early as the late 1800s. Differences may occur using the same capillary, the same capillary batch, or from batch to batch. However, if the electro osmotic flow is sufficiently high, the total dispersion is increased because of the tayloraris contribution. Electro osmotic flow, the driving of fluid at nano or micro scales with electric field, has found numerous applications, ranging from pumping to chemical and biomedical analyses in microdevices.
In normal capillary electrophoresis, anions will migrate in the opposite direction to the electro osmotic flow and their velocities will be smaller than the electro osmotic velocity. In this paper, the effect of buffer ph on the control of electroosmotic flow by applied radial voltage is examined. However, capillary electrophoresis channels are usually made of fused silica which has a large negative zeta potential and sustains strong electroosmotic flow. Jun 20, 2019 although it may seem intricate at a first glance, capillary electrophoresis is an instrumental technique with very simple principles.
Fluid mechanics of electroosmotic flow and its effect on band. It is shown that in a certain range of parameters, the electro osmotic flow can actually reduce the total dispersion by delaying the formation of a concentration shock. Electro osmotic force is a result of the electrical double layer, which develops on the wall of the capillary and induces a flow by its motion towards the cathode. To ensure that a system is properly controlled, it is often necessary to measure the eof. Potential applications of this effect could benefit from a flexible control of electro osmatic flow, for example by capillary electrophoresis in separation science 4. The tube extends between two buffer reservoirs that also hold pt electrodes. Prince technologies introduction to capillary electrophoresis. Basic theory of capillary electrophoresis microsolv.
Electroosmotic capillary flow with nonuniform zeta potential. Separation of components occurs by the simultaneous effect of the electrophoretic and electroosmotic forces that develop inside the capillary. Electroosmotic flow eof is widely used in microfluidic systems. Two categories of interfaces can be distinguished for the hyphenation. The predictability and constancy over time of the electroosmotic flow in microchannels is an important consideration in microfluidic devices. The capillary electrophoretic system uses a refillable polymer that both coats the capillary wall to suppress electro osmotic flow and acts as the sieving matrix. The electroosmotic flow eof is generated when electrodes are placed in the. Capillary electrophoresis separation method carried out in a bufferfilled capillary tube that is typically 10 to 100. Our model not only considers the temperaturedependent thermophysical and electrical properties but also includes ion thermodiffusion. The present work is an analytical and experimental study of electroosmotic flow eof in cylindrical capillaries with nonuniform wall surface charge zetapotential distributions. The addition of 8 m urea to the polymer solution, as in slab gel electrophoresis, is insufficient to fully denature some anomalously migrating ssdna fragments in this capillary. Here, we report an analysis of the thermal effect on eof under an imposed temperature difference. In most cases the electrophoretic migration of species is also accompanied by a bulk electro osmotic flow in the capillary due to the presence of a zetapotential at the capillary wall.
Capillary zone electrophoresis cze was designed to separate species based on their size to charge ratio in the interior of a small capillary filled with an electrolyte. These silanol groups possess isoelectric point pi of 1. Capillary electrophoresis has grown to become a collection of a range of separation techniques which involve the application of high voltages. Ionic origin of electroosmotic flow hysteresis scientific.
The heart of capillary electrophoresis ce is electroosmotic flow eof. Once inside the capture radius rc the polymer experiences a force due to electrophoretic and electroosmotic effects. Electroosmotic flow eof usually accompanies electrophoretic migration of charged species in capillary electrophoresis unless special precautions are taken to. Unlike gas chromatography gc, there is no pressurized gas acting as the mobile phase in ce. Model and simulate onedimensional steady state electroosmotic flow in a circular capillary under an. The sample is introduced into one end of the tubing, and a. The electro osmotic coupling is so large that it can not be ignored in discussing the mechanism of water transport in epithelia. Capillary electrophoresis the heart of capillary electrophoresis ce is electroosmotic flow eof. Therefore, the use of one dedicated capillary for each. Minute capillaries are used for the electro kinetic separation. Interac tions also exist between the capillary wall, the buffer, and the sample, as if the capillary wall had a memor y effect or hysteresis effect.
The coupling of capillary electrophoresis with electrospray ionization mass spectrometry is challenging due to the requirement of two individual electrical circuits, varying flow rates in the separation capillary, and direction of the electroosmotic flow. The study is relevant to electrophoresis in haemotology, electrohydrodynamic therapy and biomimetic electro osmotic pumps. The basic instrumental setup consists of a high voltage power supply 0 to 30 kv, a fused silica sio2. In high performance liquid chromatography hplc and gas chromatography gc the separating force is the difference in affinity of the sample components to a stationary phase, and or difference in boiling point. Capillary electrophoresis ce is a family of electrokinetic separation methods performed in submillimeter diameter capillaries and in micro and nanofluidic channels. Capillary electrophoresis capillary electrophoresis ce is a family of related techniques that employ narrowbore 20200 m i. Cec, capillary electrochromatography the acronym hpce high performance capillary electrophoresis was appointed to capillary electrophoresis and is somewhat misleading in that the term is very similar to hplc. Measurement of electroosmotic flow in capillary and microchip. Cze provides unusually high resolution since several peakbroadening effects present in traditional hplc are absent. Apr 01, 2012 this paper generalizes the analysis presented in an earlier paper gc where the effect of electromigration dispersion in the absence of any bulk flow was considered.
Analytical study of electro osmosis modulated capillary. Capillary electrophoresisanalysisof species variationsin. Jh may become pronounced for applications with high. Capillary electrophoresis ce is an instrumental evolution of traditional electrophoretic techniques, where separation occurs in fusedsilica capillaries and involves application of high voltages across buffer filled capillaries in order to achieve separation. Improved singlestrand dna sizing accuracy in capillary. Thus there is no valid reason for ignoring electro osmotic effects. Adsorption of charged species at the wall could modify this zetapotential in a nonuniform manner. Electroosmotic dispersion in a circular tube with slipstick.
Micromachined porous polymer for bubble free electroosmotic pump. When a charged particle is put in contact with a liquid in a capillary tube, a doublelayer. Very often, ce refers to capillary zone electrophoresis cze, but other electrophoretic techniques including capillary gel electrophoresis cge, capillary isoelectric focusing cief, capillary isotachophoresis and micellar. Capillary electrophoresis electrophoresis is a separation technique based on the differential transportation velocities of charged species in an electric field through a conductive medium. Fluid mechanics of electroosmotic flow and its effect. Electroosmotic flow an overview sciencedirect topics. A common cause for alteration of the flow is the adsorption of analytes to channel walls, for example, during capillary electrophoresis of proteins. Fieldeffect electroosmosis a new dimension in capillary zone. An important application of electroosmotic flow is capillary electroosmosis, where an. Electroosmotic pumps with electrochemically active. Effects of buffer ph on electroosmotic flow control by an. Capillary electrophoresis principles and applications. Effect of analyte adsorption on the electroosmotic flow in.
Feb 14, 2014 capillary electrophoresis the principle behind electrophoresis is that charged molecules will migrate toward the opposite pole and separate from each other based on physical characteristics. Electroosmotic capillary flow with nonuniform zeta. The eof is generated by the multiple ionization of silanol groups on the inner surface of a silica capillary. Request pdf fluid mechanics of electroosmotic flow and its effect on band broadening in capillary electrophoresis electroosmotic flow eof usually. A comparative study of train wave propagation and single wave propagation is presented under the effects of thickness of edl and external electric field. Electroosmotic flow or electroosmotic flow, often abbreviated eof. Oscillatory electro osmotic flow through a slit channel with slipping stripes on walls henry c w chu and chiuon ng electro osmotic flow through a thin channel with gradually varying wall potential and hydrodynamic slippage chiuon ng and qi zhoujoule heating effects on peak broadening in capillary zone electrophoresis xiangchun xuan and. Electrophoretic force and flow is a result of the applied potential difference high voltage between two ends of the capillary. Electrophoresis is performed in narrow bore 25150 m id, fused silica capillaries operates in aqueous media small sample volume required 1 to 50 nl injected high voltages 10 to 30 kv and high electric fields 100 to vcm are applied across the capillary high resistance of the capillary limits current generation and internal heating.
Effects of buffer ph on electroosmotic flow control by an applied radial voltage for capillary zone electrophoresis. The response in pumping characteristics axial velocity, pressure gradient or difference, volumetric flow rate, local wall shear stress to the influence of electroosmotic effect. If the detection modeis basisof each components electro of the two forces,electrophoretic optical, the capillary itself isused phoretic mobility. This term was given to capillary electrophoresis by chromatographers but it is not similar to hplc in the separation mechanism. A series of experiments are presented to determine the magnitude of this effect. Capillary electrophoresis yields highspeed highresolution separation on exceptionally small sample volumes it separate ionic species by their charge and frictional forces. The electrophoretic mobility is dependent upon the charge of the molecule, the viscosity, and the atoms radius. Capillary electrophoresis ce is one of the possible methods to analyse complex samples. Conclusions regulation of eof by an addition of ttab and ctab is not recommended due to a strong memory effect. Experiments began with the use of glass u tubes and trials of both gel and free solutions. These separations are facilitated by the use of high voltages, which may generate electroosmotic and electro.