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Study On High-pressure Electroosmotic Pump And Its Application In Microcolumn Liquid Chromatography

Posted on:2004-05-17Degree:DoctorType:Dissertation
Country:ChinaCandidate:L X ChenFull Text:PDF
GTID:1101360122975133Subject:Analytical Chemistry
Abstract/Summary:PDF Full Text Request
The packed-bed electroosmotic micropump (EOP, for short), utilizing the electric-actuated electroosmotic flow for fluid delivery, is a new technique appearedin the late 1990th. The EOP is the only pump that can produce high pressure and constant flow at micro-flow rate range among all the micro-sized pumps reported so far. The advantages of the EOF are: no moving parts and motors, no pistons and check valves, no dynamic sealing, no material failure or wear out. Simple in structure and flexible in design are the characteristics of EOF, which is a technological breakthrough in miniaturized liquid pumps.Based on the theory of the electric double layer, capillary electrochromatography (CEC), electrophoresis (CE) and the liquid chromatography column, the theory of the packed-bed electroosmotic pump is established. The relationship between pressure and flow rate generate in EOP is quantitatively interpreted. Factors arfecting the output pressure and flow rate of the EOP are discussed.A prototype electroosmotic pump is constructed and evaluated by experiments. The EOP consists of three packed capillary columns in parallel, spaced electrodes, a high voltage power supply and a gas-releasing device. Factors affecting the output pressure and flow rate of the EOP, including zeta potential ?electric field strength E, length of the column L, cross-section area of the column A, dielectric constant ?and viscosity coefficient n of the liquid being pumped, are analyzed. The conditions for controlling the pressure and obtaining the stable adjustable flow rate are summarized. The pump could generate output pressure as high as 20 MPa and constant flow ratelower than 20μL/min. The pump is used for manipulating the mobile phase for microcolumn liquid chromatography.The principle of multi-stage EOP is put forward hi order to achieve high -pressure output and low voltage supply in the microsystem. The output pressure PEOP (n) of an n-stage EOP is nx PEOP(?) of a single EOP under the same driving voltage. It is a paradox from the point of views either of electronics or electrochemical. It is really a novelty idea, as a result of combination of the knowledge of electroosmotics, electrical circuit and dynamics of liquid.For a long time it has been a worldwide recognized limit for the particle size packed in a electroosmotic channel, which should be larger than 50nm in order to generate electroosmotic flow. We break the limit by using 10 nm particles packed in the EOP channel, which can generate 40 MPa and flowrate of 2μL /min. The EOP can be used for mobile phase delivery in capillary HPLC. The EOP could generate pressure over 100 MPa theoretically, but we cannot realize the forecast due to the restriction of the experimental materials and the measurement instrument.
Keywords/Search Tags:electroosmotic pump, packed-bed column, capillary liquid chromatography
PDF Full Text Request
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