Study Of Capacitively Coupled Contactless Conductivity Detector And Its Applications In Capillary Electrophoresis

Capacitively coupled contactless conductivity detection (C₄D) based on themeasurement of an AC signal from detection electrodes was studiedsystematically. The C₄D completely overcame the disadvantages of electrodesfouling and interference of separation voltage on measurement signal in CE.A new equivalent electronic circuitry for detection cell was established whichcan describe a relation between signal response and the cell parameters, andsimplified theoretical equations were also given for CE and capillary LC detection.A C₄D detector was constructed and evaluated. The effects of parameters of thedetection cell and AC signal on signal response of the detector were discussedsystematically. A CE system with C₄D detector was used for analysis of inorganicions and organic acids and LOD of μmol/L were obtained. A method wasdeveloped for analysis of trace heavy metal ions by CE-C₄D with field-amplifiedinjection and LODs of nmol/L were reached. A combined detector involvinglight-emitting diode-induced fluorescence and C₄D was completed for thesimultaneous determination of fluorescence and ionic analytes.Electroosmotic pump (EOP), utilizing electroosmotic flow drives fluid flow, isa new technique appeared in recently years. It has characteristics of simpleconfiguration without moving parts, wide range of flow rate, and is ideallysuitable for delivery liquid in micro-fluidic flow analysis systems. A low-pressuresmall electroosmotic pump capable of generating a flow rate of 360 μL/min wasconstructed and evaluated. Bubbles produced on electrodes and in electroosmoticcolumn were instantly removed from the pump. It can work continuously over oneweek without any decrease of efficiency. The pump is useful n flow injectionanalysis and micro-reactors. The online measurement of oxygen content is necessary in the process of theproduction and the use of high gases. The previous methods have disadvantages ofperiodical maintenance and calibration. A new type of catalytic oxygen sensorbased on the measurement of the hydrogen-oxygen reaction heat has beenconstructed and evaluated. The characteristics of the sensor are: 90 % responsetime 5 s, linear response from 1 to 1200 ppm with 1 ppm LOD, high sensitivityand excellent response stability. It is suitable for on-line mornitoring of oxygencontent in inert gases, and permanent gases.