Study And Application Of PDMS/PDMS Thin Film Microchip Electrophoresis-contactless Conductivity Detection

Objective:In this experiment,poly（dimethylsiloxane）（PDMS）microchannel substrate was prepared by Du Pont dry film lithography and PVC frame method.PDMS microchannel substrate and PDMS film were reversibly combined to form PDMS/PDMS film microchip electrophoresis system.Combining with the contactless conductivity detection system（C⁴D）,a set of PDMS/PDMS thin film microchip electrophoresis-contactless conductivity detection system（MCE-C⁴D）with simple operation,high speed,high efficiency and high sensitivity was established.The system can realize the rapid detection of aminoglycosides,provide a simple method for the analysis of antibiotics,and also detect inorganic anions in tap water and Xiangjiang river water,laying a foundation for the real-time online monitoring of anions in tap water and Xiangjiang river water.Methods:（1）Using Du Pont dry film lithography and chemical etching to prepare the mould of microchannel substrate,and CNC engraving method to prepare Poly vinyl chloride,PVC)frame;The prepared PVC frame is attached to the front of the microchannel substrate mold to obtain the microchannel substrate mold with PVC frame.The PDMS microchannel substrate with smooth surface,uniform size and uniform thickness was obtained by pouring PDMS on the surface of microchannel substrate mold.The activated PDMS microchannel substrate is bonded with PDMS film,and a set of MCE-C⁴D detection system for PDMS/PDMS film is constructed by combining C⁴D system,and its feasibility is analyzed.（2）By optimizing the factors affecting the separation and detection performance of PDMS/PDMS thin film MCE-C⁴D detection system,including the thickness of PDMS thin film,injection time,concentration ratio of buffer solution,concentration of buffer solution,etc.,the best analysis conditions were obtained,and the separation and detection of metal cations（K⁺,Na⁺,Li⁺）were successfully realized,and antibiotics such as aminoglycosides were quickly detected by using this system.（3）In addition,under the condition of changing the voltage polarity,the separation and detection conditions of anion PDMS/PDMS thin film MCE-C⁴D detection system were optimized,including the concentration of tetradecyl trimethyl ammonium bromide（TTAB）,the concentration ratio of buffer solution,the concentration of buffer solution,etc.,to obtain the best analysis conditions.The separation and detection of single anion(PO₄^3-)and mixed anion solutions(Cl^-,SO₄^2-,PO₄^3-)were successfully realized,and the optimized PDMS/PDMS thin film MCE-C⁴D detection system was used to separate and detect inorganic anions in tap water and Xiangjiang water,thus realizing the quality monitoring of water quality.Results:（1）The mould of microchannel substrate prepared by Du Pont dry film lithography and chemical etching is complete and smooth,which meets the quality requirements of PDMS microchip.PDMS microchannel substrate prepared by frame method has a complete and smooth surface,uniform size and uniform thickness,which meets the quality requirements of microchip electrophoresis laboratory.Under the buffer system of 10 m M morpholine ethanoic acid-L-histidine（MES-His）（1:1）,PDMS/PDMS thin film MCE-C⁴D detection system successfully separated and detected three metal cations（K⁺,Na⁺,Li⁺）,which met the requirements of feasibility analysis.（2）By optimizing the separation and detection conditions of cation PDMS/PDMS film MCE-C⁴D detection system,including the thickness of PDMS film,injection time,concentration ratio of buffer solution,concentration of buffer solution,etc.,the standard samples of1 m M mixed metal cations（K⁺,Na⁺,Li⁺）were separated and detected.The response peak height,ignal-to-noise ratio（S/N）and theoretical plate number（N）and s of three metal cations（K⁺,Na⁺,Li⁺）were obtained.The influence of separation and detection conditions on the system performance was comprehensively evaluated,and the best separation and detection conditions were obtained:the thickness of PDMS film was 25μm;Sample injection time,2 s;Buffer solution,10 m M MES-His（1:1）.Under the optimal analysis conditions,three metal cations（K⁺,Na⁺,Li⁺）were successfully separated and detected within 80 s,and the detection limits were 16.6μM,18.5μM and 10.2μM,respectively.Based on the established PDMS/PDMS thin film MCE-C4D detection system,the aminoglycoside antibiotics were successfully detected within 60 s.（3）By optimizing the separation and detection conditions of anion PDMS/PDMS thin film MCE-C⁴D detection system,the best separation and detection conditions were obtained:TTAB concentration,0.5 m M;Buffer solution,10Mm MES-His（1:1）.Under the optimal analysis conditions,single anion(PO₄^3-)and three mixed anions(Cl^-,SO₄^2-,PO₄^3-)were successfully separated and detected within 60 s.The detection limit of single anion(PO₄^3-)is 25.46 mg/L,and the detection limits of three mixed anions(Cl^-,SO₄^2-,PO₄^3-)are 51.99 mg/L,49.86 mg/L and 45.36 mg/L,respectively.Based on the established PDMS/PDMS thin film MCE-C⁴D detection system,the real-time detection of inorganic anions in tap water and Xiangjiang river water was successfully realized.Conclusion:（1）PDMS microchannel substrate was successfully prepared by Du Pont dry film lithography and PVC frame method.PDMS microchannel substrate and PDMS thin film were reversibly combined to form PDMS/PDMS thin film microchip electrophoresis system.By combining with C⁴D system,a PDMS/PDMS thin film MCE-C⁴D system with simple operation,high speed,high efficiency and high sensitivity was established.（2）The established PDMS/PDMS thin film MCE-C⁴D system has the advantages of simple operation,rapid reaction and high sensitivity,successfully realizes the separation and detection of heavy metal cations,and has been successfully applied to the rapid detection of aminoglycosides.（3）At the same time,under the condition of negative voltage,The anion PDMS/PDMS thin film MCE-C⁴D system has been established.This system has been successfully applied to the detection of inorganic anions in tap water and Xiangjiang River water,providing a reliable analysis method for water quality monitoring.In a word,with the continuous development of microchip electrophoresis-contactless conductivity detector,the performance of the established PDMS/PDMS thin film MCE-C⁴D system is better,and it will play a great role in clinical medicine,drug analysis,environmental analysis and food safety.28 pictures,10 tables and 55 references.