When a current is applied, this leads to joule heating. In the last years computer simulations have begun to be also applied in different instances of microfluidics, especially in microchip electrophoresis where an electrophoresis process takes place in the microcapillaries manufactured on the surface of the small. T is the temperature difference, r c is the radius of the capillary, i is the thermal conductivity of the solution, r x is the distance from the capillary wall, and g is the heat generation rate wm3. Ce uses tubes 20100mm diameter and 20100 cm in length. In this paper, a rigorous mathematical model is developed to describe the joule heating and its effects on electroosmotic flow and mass species transport in microchannels.
The proposed model includes the poisson equation, the modified navier. Electrophoresis is a separation technique based on. When current passes through a solution, electrical energy is partially converted into joule heating figure 1. Background to capillary electrophoresis capillary electrophoresis is usually said to date from 1981, when jorgenson and lukacs described spectacular separations of peptides using free zone electrophoresis in glass capil laries of 75jlm i. It presents the best methods, hints and tips for core procedures such as one dimensional. The basic instrumentation for capillary electrophoresis is shown here and includes a power supply for applying the electric field, anode and cathode compartments containing reservoirs of the buffer solution, a sample vial containing the sample, the capillary tube, and a detector. The ionic liquid 1butyl3methylimidazolium tetrafluoroborate was used as modifier to improve the separation efficiency. The temperature difference between the capillary wall and any radius within the capillary is given by where. The baseline features are due to joule heating and is an intrinsic property of the proprietary gel buffer. However, early attempts to use electrophoresis as an analytical tool were persistently frustrated by the existence of joule heating, which acts to discount the electrophoretic effect. A mix of known proteins used for testing buffer matrices in sciex kits.
Micellar solutions exhibit a relatively high conductivity, so a capillary with small diameter could be the right choice to prevent excessive joule heating. For use on the pace mdq and pa 800, and cesi 8000 series systems qty 1. Coolant refill utilized to dissipate joule heating in capillary electrophoresis and provide greater reproducibility injection to injection. Thus a way of combatting the thermal effect during the electrophoretic process was needed.
Capillary electrophoresis the basics electrophoresis in a buffer filled, narrowbore capillaries each capillary is about 25100. Joule heating effects in capillary electrophoresis designing electrophoretic microchips. In capillary zone electrophoresis, analytes are separated in a capillary containing only buffer without any anticonvective medium. In addition, sample species transport in a microcapillary is also investigated by numerically solving the mass transfer equation with consideration of temperaturedependant diffusion coefficient and electrophoresis mobility. 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. Length varies based on application but is normally in the 2050 cm range. Temperature increase in capillary electrophoresis ce due to joule heating is an inherent limitation of this powerful separation technique. Capillary electrophoresis capillary electrophoresis ce is a family of related techniques that employ narrowbore 20200 m i. In the biotechnology industry, traditional sodium dodecyl sulfatepolyacrylamide gel electrophoresis sdspage has been widely used to monitor the integrity and purity of therapeutic proteins during formulation and process development, and for lot release and stability testing.
Unlike gas chromatography gc, there is no pressurized gas acting as the mobile phase in ce. And because the capillary is rather rugged, elaborate rinsing procedures are possible so that the capillary can be refilled and reused. For example, at e 0 36 kvm, the average fluid temperature in the main part of the capillary is increased by only 5% from 298 to 3. Previous studies on joule heating and its effects on electroosmotic. Peptide mapping and analysis using capillary electrophoresis. Pdf joule heating effects in capillary electrophoresis. Introduction the term electrophoresis is generally applied to the movement.
During the electrophoresis, the joule heating causes a temperature rise and temperature gradients in the buffer solution. Joule heating effects in capillary electrophoresis. The elevated liquid temperature may on one hand denature live biological samples, while on the other be exploited in heatrelated physicochemical processes, for example, the thermal. Joule heating is a consequence of the resistance of the solution to the flow of current. Capillary electrophoresis is a physical method of analysis based on the migration, inside a capillary, of charged analytes. Electrophoresis download ebook pdf, epub, tuebl, mobi. Article pdf available december 2009 with 447 reads. Karczemska, joule heating effects in capillary electrophoresis designing electrophoretic microchips, journal of achievements in materials and manufacturing engineering 372 2009 592597. The capillary walls used in ce must dissipate efficiently. Joule heating in capillaries and columns used in electrodriven separation techniques such as capillary electrophoresis ce and capillary electrochromatography cec are know to affect the electroosmotic flow eof, retentionelectrophoretic interactions, diffusion of analytes, and ultimately the efficiency and reproducibility of the separation. Experimental all ce experiments were performed using an agilent capillary electrophoresis system from agilent technologies. Experimental studies of joule heating effects in electroosmotic thermofluid mechanics include cetin and li 32 for electrophoresis fusedsilica capillary reactors, by rathore 33 for open. Fast analyticalscale separations by capillary electrophoresis and liquid chromatography robert t. Joule heating effects on separation efficiency in capillary zone electrophoresis with an initial voltage ramp.
Capillary electrophoresis wikimili, the free encyclopedia. Based on tayloraris dispersion theory, a general analytical formula was derived for the theoretical plate height in capillary zone electrophoresis with the consideration of joule heating effects. Effect of joule heating on electrokinetic transport. Effect of joule heating on electrokinetic transport cetin. A longer capillary can be useful in the case of large amount sample solutions to obtain a better separation at the expense of time. Feb 07, 20 micellar solutions exhibit a relatively high conductivity, so a capillary with small diameter could be the right choice to prevent excessive joule heating. In this technique, the proteins are bound to sds at a ratio of 1. Diffusion, joule heating, and band broadening in capillary gel. Temperature distributions occurring during capillary electrophoresis because of joule heating effects will be calculated with use.
Hvit if the heat is not sufficiently dissipated from the system the resulting temperature and density gradients can. Joule heating effects on separation efficiency in capillary zone. A model for joule heating induced dispersion in microchip electrophoresis yi wang,a qiao lina and tamal mukherjeeb. They found that with the inner diameter of the capillaries scaled down to 80 m, voltages as high as 30 kv could be applied without incurring overheating problems. Using a small id and having a thick wall reduces this problem. Capillary electrophoresis ce has gained widespread adoption in biopharmaceutical industry as a. In capillary electrophoresis ce joule heating has been long known. Pdf joule heating effects in capillary electrophoresis designing. Universal method for determining electrolyte temperatures. A model for joule heatinginduced dispersion in microchip. Modeling of electroosmotic flow and capillary electrophoresis. Aug 04, 20 joule heating is a problem because it changes the buffer solutions viscosity, with the solution at the center of the capillary being less viscous than that near the capillary walls. Capillary electrophoresis is a physical method of analysis based on the migration, inside a capillary, of charged analytes dissolved in an electrolyte solution under the influence of a directcurrent electric field. Joule heating is a ubiquitous phenomenon in electrokinetic flow.
Longitudinal diffusion is the main source of bandbroadening. The main advantage of performing electrophoresis in narrowbore capillaries is reduction of the effects of. Diffusion, joule heating, and band broadening in capillary. Capillary electrophoresis is performed in a submillimeter diameter tube, called a capillary, which contains a flowing electrolyte solution. Joule heating effects in capillary electrophoresis journal of.
Unlike high performance liquid chromatography hplc these is no high pressure pumped mobile phase. Capillary electrophoresis, or ce, is a technique used in chemical analysis to separate molecules in an electric field according to size and charge. Capillary electrophoresis is a physical method of analysis based on the migration, inside a capillary, of analytes dissolved in an. Universal method for determining electrolyte temperatures in. When uv detection is used in this method to monitor separation. During the electrophoresis, the joule heating causes a temperature rise. Capillary electrophoresis in clinical chemistry david perrett. A milestone for columnbased electrophoresis was set in the early 1980s, when jorgenson et al. The characteristics of the joule heating, electroosmotic flow, and sample species transport in microcapillaries are. Capillary electrophoresis ce is a family of electrokinetic separation methods performed in submillimeter diameter capillaries and in micro and nanofluidic channels. Active cooling systems can decrease the temperature of a large part of the capillary but they leave hot spots at the capillary ends which can completely ruin some ce analyses despite their short lengths.
The transverse and longitudinal diffusion coefficients are roughly equal for regular field intensities, but the former dominates for the high field intensities normally used for capillary gel electrophoresis ce. However, an increase in the voltage used can cause excessive. Joule heating effects on peak broadening in capillary zone. Jh may become pronounced for applications with high electrical potential gradients or with high ionic concentration buffer solutions. An increase in ph increased the negative charge of the analytes, which, in turn, favored a greater affinity for the buffer and a higher complexation between borate and phenols 18. Our results indicate that both diffusion coefficients increase with the electric field intensity. 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. A method of nonaqueous capillary electrophoresis based on ionic liquids was developed with a high electric field 800 vcm. A joule heating plot is useful in optimizing the applied voltage. The production of heat in ce is the inevitable result of the application of high field strengths. Therefore, joule heating induced fluid temperature increase can enhance the throughput and reduce the separation time of capillary electrophoresis.
Joule heating results from the fact that the heat generated inside the capillary by the passage of current through it can only be dissipated at the surface, causing a radial temperature gradient across the capillary that compromises separation. The migration velocity of the analyte under an electric field of intensity e is determined by the electrophoretic mobility of the. The capillary format offers a number of advantages. In particular, knox and grant17,18 investigated jhinduced tayloraris dispersion of electrophoresis in a circular capillary, while cifuentes and poppe19 studied steadystate jhinduced dispersion in a rectangular capillary that is assumed to have an in. We calculated the longitudinal and transverse diffusion coefficients for a dna molecule undergoing gel electrophoresis in the limit where. Because a solutes electrophoretic mobility depends on viscosity, solute species in the center of the capillary migrate at a faster rate than those near the. Comparison of air and liquid cooling in capillary electrophoresis. Computer simulations are widely used for designing, which contributes to a cheaper equipment developing process. Application of capillary zone electrophoresis methods for the. The system comprises a ce unit with builtin diode array detec. The loss of peak resolution is often referred to as zone broadening in ce.
High performance capillary electrophoresisan introduction 5968. Capillary electrophoresis principles and applications. The heat produced, h, is directly proportional to the applied voltage between. Because a solutes electrophoretic mobility depends on viscosity equation \ref12. Peak resolution in capillary electrophoresis is dependent on many variables, including longitudinal diffusion, injection length, sample adsorption to capillary walls, electrodispersion, joule heating, and detector cell size. Electroosmosis, separation efficiency, and joule heating detection methods indepth discussion of the separation principles and capabilities of the major modes of ce sieving gel electrophoresis isoelectric focusing free solution ce. This book is designed to help you make the most of your ce separations, and includes comprehensive information on. Joule heating is a problem because it changes the buffer solutions viscosity, with the solution at the center of the capillary being less viscous than that near the capillary walls.
Analytical study of joule heating effects on electrokinetic. We also acknowledge previous national science foundation support under grant numbers 1246120, 1525057, and 14739. The joule heating jh is a ubiquitous phenomenon in electrokinetic flow due to the presence of electrical potential gradient and electrical current. Further details are discussed in the results and discussion section of this note. Temperature distributions occurring during capillary electrophoresis because of joule heating effects will be calculated with use of the coventorware software. Capillary electrophoresis is fundamentally limited by joule heating causing radial temperature gradients and therewith velocity differences across the cross section of the capillary occur that disperse the analyte zone during separation. Capillary electrophoresis using narrow bore tubes, ce removes the joule heating effect, which decreases band broadening, giving faster separations than gel. Computer simulations with the model of capillary, with the same geometry as the. The joule heating depends on the inverse square of the capillary. Nov 21, 2003 joule heating is present in electrokinetic transport phenomena, which are widely used in microfluidic systems. Instrumentation for capillary electrophoresis image and. A model for joule heatinginduced dispersion in microchip electrophoresis yi wang,a qiao lina and tamal mukherjeeb. Ionic liquids as modifiers to improve the separation. Hvit if the heat is not sufficiently dissipated from the system the resulting temperature and density gradients can reduce the separation efficiency.
High performance capillary electrophoresis agilent. This internal heat source can lead to significant increase and nonuniformity in liquid temperature. The separation time is inversely proportional to applied voltage. Joule heating is present in electrokinetic transport phenomena, which are widely used in microfluidic systems. Electrophoresis is a class of separation techniques in which we separate analytes by their ability to move through a conductive mediumusually an aqueous bufferin response to an applied electric. Capillary electrophoresis the heart of capillary electrophoresis ce is electroosmotic flow eof.
Electroosmotic flow and mass species transport in a. High performance capillary electrophoresis second completely revised edition by henk h. The small bore and thickness of the silica are important. Joule heating is a problem because it changes the buffer. Method development by use of capillary electrophoresis and. Apr 19, 2014 joule heating is a ubiquitous phenomenon in electrokinetic flow. Performing gel electrophoresis in a capillary has the added advantage of direct quantitation without the need for stainingdestaining. Capillary electrophoresis is a physical method of analysis based on the migration, inside a capillary, of analytes dissolved in an electrolyte solution under the influence of a directcurrent electric field. These separations are facilitated by the use of high voltages, which may generate electroosmotic and electro. Joule heating and determination of temperature in capillary. The joule heating depends on the inverse square of the capillary radius. Diffusion, joule heating, and band broadening in capillary gel electrophoresis of dna.
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