Fabrication Of Low-cost Red Diode Laser Induced Fluorescence Detector And Its Application In Microchip Electrophoresis Analysis

Laser induced fluorescence(LIF)detector has the characteristics of high sensitivity,fast response speed,suitable for miniaturization and integration,which can be easily combined with microfluidic chips.Commercial laser-induced fluorescence(LIF)detectors are expensive.The use of low-cost components to build LIF detectors will be helpful for the development of low-cost,portable microchip electrophoresis devices and promote its practical application.The microchips used in microchip electrophoresis can be fabricated with glass and plastic materials.Compared with glass microchips,plastic microchips have the advantages of low cost and easy fabrication,but the background fluorescence of plastic microchips is usually higher than that made of glass.Cyclic olefin copolymer(COC)itself has low autofluorescence,but during the fabrication process,it is still possible to cause evident increase of the background fluorescence.Since the autofluorescence decrease significantly with the increase of excitation wavelength,the laser induced fluorescence detector built with red laser diode can avoid influence of the background fluorescence caused by microchip material.The aim of this thesis is to build a low-cost red diode LIF detector that can be used in microchip electrophoresis for the separation and detection of biogenic amines and the selection of reaction conditions of the synthesis of azaacenes based red fluorescence materials.1.A low-cost confocal 635 nm red diode LIF detector was built.The red laser diode has the advantages of low cost and stable power,and because its laser wavelength is in the red light region,it can avoid the background fluorescence caused by the plastic microchip material.At present,some researchers have chosen red laser diodes to build LIF detectors,but some of the components used are relatively expensive.Our aim is to find alternative cheap and easy-to-obtain components to build a low-cost LIF detector.The 635 nm laser diode was used as the excitation light source,and the low-cost and widely available domestic OD3 filter was used in a combination way,the low-cost avalanche photodiode(APD)(AD500-8 TO52S1)was used as the photoelectric conversion device,and a confocal optical configuration was selected to build a low-cost red diode LIF detector,and a detection limit of 0.10nmol/L for methylene blue is obtained,which is similar to that with the imported OD4 filter.The prepared red diode LIF detector has advantages of simple structure and low cost,can be used for microchip electrophoresis analysis to avoid the influence of background fluorescence of plastic microchips.2.The 635 nm diode LIF detector was used for the analysis of biogenic amines with microchip electrophoresis.Plastic microchip electrophoresis has the advantages of fast analysis speed and less consumption of samples and reagents,but the background fluorescence of plastic microchip is relatively high.On the other hand,the composition of beer is normally complex,so the background fluorescence can be a problem too.We tried to use a LIF detector excited by the red light for the electrophoresis analysis with COC microchips.Beer was selected as the real sample.Three kinds of biogenic amines(tryptamine,histamine and spermine)were labeled with red fluorescent dye Cy5,and the microchip was dynamically modified with anionic polymer polyacrylic acid.Under the separation condition with the presence of acetonitrile,the three types bio-amine could be separated around 30 s.The detection limits of histamine and spermine are 0.9 nmol/L and 2.3 nmol/L,respectively,which meet the actual detection requirements for these two biogenic amines.3.A 635 nm red diode laser induced fluorescence detector was used to screen the synthesis conditions of azaacenes based red fluorescence materials by microchip electrophoresis.In the process of material synthesis,the composition of the material can be complex,its yield is normally dependent on the reaction conditions.The characterization of materials is generally performed with thin layer chromatography or column liquid chromatography,the analysis time ranges from a few to dozens of minutes.The microchip electrophoresis can finish a separation within a minute.In this work,we used microchip electrophoresis to quickly evaluate the synthesis condition of fluorescent materials.Using three azaacene-based red fluorescence materials,DHTAP,dimethyl DHTAP,and nitrophenyl DHTAP as the model,we investigated the influence of synthetic conditions.The time needed for a single separation was within30 s.The results show that sodium chloride as a carrier can increase the yield of these products,and the yield of DHTAP can be close to 100%,which indicates that microchip electrophoresis is a potential tool for rapid screening of reaction conditions of fluorescent materials.