| Capillary electrophoresis(CE)and microchip electrophoresis(MCE)are important micro separation based analytical techniques,which can be applied in fields such as environment,food safety,medicine and pharmacy.With the rapid development of science and technology,CE and MCE instruments are getting the features of miniaturization,integration and automation.MCE is an ideal tool for rapid on-site analysis of multiple components,while the miniaturized CE devices can be one of the prerequisites for its wide application in real analysis.However,there are limited number of miniaturized CE/MCE equipments commercialized.These miniaturized separation based analytical instruments may be expensive,which is an apparent obstacle for their wide application.Meanwhile,compromises among the sensitivity,extent of miniaturized and the cost may also be one of the factors affect their application in real-world analysis.Based on previous works,this dissertation aims at the exploration of novel CE/MCE devices by the selection of widely available optical and electronic parts,utilization of 3D printing techniques for miniaturized structures and careful design of the whole devices to improve the integration and reduce their cost.This dissertation mainly consists of following innovative works:(1)By using optical and electronic components that are widely available as main stream industrial products as the main parts of laser-induced fluorescence(LIF)detector,taking advantage of the convenience of 3D printing for rapid processing of complex structures,a miniaturized LIF detector module was fabricated through the optimization of the optical structure to obtain high sensitivity and maintain a low-cost.(2)Based on the original structure of MCE system in the laboratory,a handheld MCE analyzer was built with the micro LIF detector module.The sample injection unit,high-voltage unit and data acquisition and control unit were integrated into the device with a dedicated,computer program.Its performance was proved and actual sample analysis was performed.(3)A low-cost strategy for multichannel high-voltage power supply for MCE was proposed.The strategy could realize the real-time control of each high-voltage output independently,the number of the output could be easily expanded.(4)Based on the structural characteristics of the micro LIF module,the structure of power supply and signal acquisition of the module were optimized to build a multi-channel capillary detector with independent photoelectric detection units.Its performance was proved by test samples.(5)The low-cost computerized numerical control(CNC)engraving machine was modified to realize the automatic injection through its high precision 3D motion control.An automatic multi-channel CE instrument was built that could automatically fulfill the operations of sample injection,separation and capillary flushing.This dissertation consists of six chapters.Chapter 1:The development history,basic principle,composition and application of CE/MCE analysis system is introduced.The miniaturized analytical equipments and high-throughput detection devices used in CE/MCE are summarized.The challenges of CE/MCE devices in the application of real-world analysis are discussed,and the objective of this research and its significance are summarized.Chapter 2:The laser diode,aspheric lens and avalanche diode(APD)were used as the excitation light source,the convergent lens and the photoelectric sensor,respectively.These components were arranged in a 3D printed structure to form a micro LIF detection module with a size of 38×51×12 mm~3.The cost of the whole detector is only about￥330.The detection limit of the detector module tested with sodium fluorescein was 41 p M,which can meet the requirement of general fluorescence detection within microchannels.It has a great application potential in portable instruments or point of care testing(POCT)devices.Chapter 3:Taking the micro air pump as the negative pressure source,the solenoid valve as the negative pressure controller and a 3D printed structure for the negative pressure induced sample injection module for MCE.The electronics was integrated on a circuit board with a size of 78×38×18 mm~3.The micro LIF detection module,data acquisition card,negative pressure injection unit and electrophoresis high-voltage power supply were assembled into a box of 89×98×98 mm~3to construct a fully-functional,universal handheld MCE analyzer.The prepared device had a weight of 350g,could be powered by a power bank or through a laptop.A camera was built-in to facilitate the alignment of the detection point with the microchannel,without the necessity of introduction of fluorescent solution.The device was used to detect two rhodamine dyes in a 30 mm separation channel.The recoveries of spiked standards were in a range of 84.0–110%,indicating its potential for screening illegal addition of rhodamine dyes.Chapter 4:A multi-channel high-voltage power supply was built.Each channel of it could act as either DC current source or sink.The initial device contains 4 high-voltage modules upto 3000 V,each had its grounding route,allowing DC current flow in or out of the port according to the balance of the voltage settings in the network and the load resistance.Output of each channel could be independent,not switching of the polarity or grounding operation is needed to realize the change of the polarity of the current.This design simplified the device and made it encapsulated in a compact box.Its ability for electric pinched injection was confirmed,and it could also monitor the current values.The total cost of the device is about￥2300 with a size of 15.8×11.5×14.8 cm~3,which is suitable for on-site analysis.Chapter 5:A four-channel modular LIF detector was designed and built with standalone electric optical sensor for each channel.By optimizing the arrangement of functional units and power supply,share of components was realized to reduce the overall cost and the size.The detection limits of the detector measured with sodium fluorescein were between 20–60 p M,and its total cost was about￥2500.It was used as the detector of multi-channel capillary electrophoresis,which confirmed its application potential in high-throughput analysis of biological samples.Chapter 6:A commercial micro-CNC engraving machine was modified by using3D printed parts with complex internal structure to an automatic sample injector for CE.The injector could perform the pressurized rinsing of capillary and injection of certain amount of sample.The cost of the injector was less than￥1200.By integrating this injector,aforementioned LIF detector,high-voltage power supply and their operation power supply,a fully automatic multi-channel CE analyzer was built.The analyzer could be controlled by a program written with Lab VIEW.Its application potential in bioanalysis and material preparation by the separation of DNA fragments and synthesized fluorescent materials. |
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