Studies On Novel Separation And Analysis Methods Based On The Cotton Fiber Microfluidic

Microfluidic analysis based on the cotton fiber has grown up as a fast and convenient analytical method recently. In this thesis, novel separation and analysis methods based on the cotton fiber microfluidic were studied. A cotton fiber microfluidic channel device was developed firstly. Three microfluidic patterns made of cotton or cotton-polyester were designed, including a Y-shaped microfluidic channel, a microfluidic separation channel and a microfluidic triple-channel. Three corresponding methods were proposed and applied to the determination of nitrite, the separation of mixed dyes and the simultaneous determination of copper and zinc, respectively. Results showed that cotton fiber microfluidic analysis played an important role to push the development of low-cost methods for separation and analysis. This thesis consists of six parts as follows:Chapter 1:ReviewA brief review of the development of microfluidic analysis was given, which include the characteristics and processing technologies of microfluidic patterns materials, the manufacture of microfluidic devices and the research development of microfluidic. The topic of this thesis was proposed based on the review.Chapter 2:Manufacture of the Microfluidic Channel DeviceA self-made thread-based microfluidic channel device was firstly designed, which was customized to fix thread-based microfluidic channels. The device is composed of a support, loading system, reservoir devices and a microfluidic terminal fixer. Loading system, reservoir devices and the microfluidic terminal fixer are installed on the support and can be assembled and moved freely, so that the device can fit any microfluidic pattern and the wicking rate of the fluid can be controlled. Moreover, multiple loading systems can be fixed on the device so as to adapt it to any multichannel microfluidic patterns.Chapter 3:Pretreatment of ThreadThe hydrophilic pretreatment methods and conditions for the threads were investigated in this part. Compared with different methods, pretreated with the mixed solutions of sodium hydroxide and sodium dodecyl sulfate was preferable. The concentration of pretreatment solutions, pretreatment time and temperature were optimized. The results showed that the hydrophility of cotton and cotton-polyester was enhanced significantly and the wicking rate of liquid on thread was faster.Chapter 4:Determination of Nitrite Based on Y-Shaped Cotton-Polyester Thread Microfluidic ChannelA novel method based on Y-shaped microfluidic channel was firstly proposed in this study. The microfluidic channel, made of two cotton-polyester threads, was based on the capillary effect of cotton-polyester threads for the determination solutions, through which the sample solutions and the indicator can be introduced at the same time. The thread-based microfluidic channel device was used to fix the Y-shaped microfluidic channel. The spectrophotometry was compared with gray analysis colorimetric method. The former had a lower detection limit while the latter showed advantages in both convenient and fast operations and lower consumption of samples. The proposed method was applied to the determination of nitrite. The linear ranges and detection limits are 1.0 μmol/L-70 μmol/L, 0.66 μmol/L (spectrophotometry) and 50 μmol/L～450 μmol/L,45.10 μmol/L (gray analysis colorimetric method) respectively. This method has been successfully used to the determination of nitrite in soil samples and moat water with recoveries between 96.7% and 104%. It proved that the proposed method was a low-cost, rapid and convenient analytical method with extensive application prospect.Chapter 5:Separation of Dyes Based on Cotton-Polyester Thread Microfluidic ChannelCotton-polyester threads were used as a new separation carrier. A novel separation method based on the separation carrier was developed and applied to the separation of mixed dyes (Malachite Green and Rhodamine B). Effects of sample introduction methods, elution solutions and the tilt angle and length of the separation channel were evaluated. The mixed dyes could be successfully separated under the optimal conditions. It showed that cotton-polyester threads-based microfluidic channel can separated mixtures effectively.Chapter 6:Simultaneous Determination of Copper and Zinc by Microfluidic Triple-Channel and Laser Thermal Lens SpectrometrySimultaneous determination of copper and zinc using thread-based microfluidic channels is firstly developed, which is based on the wicking rate difference between cotton threads and cotton-polyester threads. The composite thread microfluidic triple-channel was made of a cotton thread and two cotton-polyester threads. A near-field laser thermal lens spectrometry (TLS) analyzer was used as the detector. The results showed that the intensity of STLS was proportional to the concentration of copper and zinc ranging from 0.3～5.0 μg/mL and 0.3～ 7.0 μg/mL with the limit of detection of 0.20 μg/mL and 0.25 μg/mL, respectively. The method has been applied to the simultaneous determination of copper and zinc in soil samples. Recoveries are between 94.0% and 106.3%.