Studies On The Cloud Point Extraction And Cotton Fiber Microfluidics Combined With Spectrophotometric Method

Sample preconcentration and separation are important research fields in analytical chemistry,and also are key procedure in analytical method.Recently,Cloud-point extraction(CPE),an easy,safe,environment-friendly,rapid and econcimic technique for preconcentration of trace metals and macromolecular compounds from aqueous solutions has recently become an attractive research field for liquid-liquid extraction.Over the last few years,thread has emerged as a promising substrate for microfluidice and separation due to their natural capillary channel.However,some technical problems still exist and prevent its application of Cloud-point extraction and thread-based microdevices,which includes the lack of highly selectivite complexing agent,thus causing interference when spectrophotometric method was applied for the determination of metals;single factor method was adopted for optimizing the conditions for CPE and the interaction between the factors was ignored;the existing methods on thread-based microdevices have almost fixed horizontally on the poly membrane,which result the solution migration only by capillary force;up to now,it appears that none of the investigations is concerned with thread-based microfluidic separation,and so on.Therefore,it is necessary to develop CPE and thread-based microfluidice to separate and preconcentrate metals and macromolecular compounds in samples.Thus,this thesis focused on the cloud point extraction and thread-based microfluidice for sample preconcentration and separation method,and carry out the following work:1)The research of complexing agent as CPE for sensing of Cu(II);2)The research of composite nanoparticles as solid phase microextraction agent combinations with CPE for sensing of Ni(II);3)The research of single factor method combinations with BBD for optimization of CPE extraction conditions,and the proposed method was applied to determine phosphate;4)A three-channel microfluidic device was designed,and the three-channel microfluidic device has been applied to pretreatment conditions for cotton fiber and separation of chloroplast pigments in spinach leaves extract;5)The three-channel microfluidic device was applied to analysis of chromium in water.The results were as follows:2’,7’-di(2-benzothiazolyl)-fluorescein was synthesized by using 2-(2’,4’-dihydroxyphenyl)benzothiazoles and phthalic anhydride.Trace Cu2+ was separated and preconcentrated with BTF as chelating agent,and octylphenoxypolyethoxy-ethanol(TX-114)as extraction agent.The effect of different variables such as pH,TX-114 concentration was investigated and optimum conditions were established.Under the optimal conditions,the absorbance value(△A)is linearly with Cu2+ concentration in the range from 0.03 to 2 μmol/L(1.90-127 μg/L).The proposed method was successfully applied to determine trace Cu2+ in water and tea samples with satisfactory results.The results given by the proposed method are in good agreement with those given by ICP-AES.The proposed method offers good selectivity and accuracy that can be applied to the determination of copper with a limit of detection of 7.48 nmol/L.Trace nickel was separated and preconcentrated with PAN as chelating agent,and TiO2/sepiolite composites-TX-114-octyl alcohol as extraction agent.Under optimal conditions,the absorbance signal is linear with nickel concentration in the range of 0.02-3 mg/L and the detection limit was 5 μg/L.The proposed method was successfully applied to the determination of nickel in natural products of Baisha green tea and Coconut water in Hainan.The results indicate that TiO2/sepiolite composites could be used as solid phase extraction matrix,combined with CPE and visible spectrophotometry for the determination of nickel.CPE is used as a concentration procedure for the determination of phosphate by spectrophotometry.The different variables of CPE were investigated by single factor experiment,and Box-Behnken Design(BBD)was adopted to further investigate the interactions of different variables.The absorbance is linearly with phosphate concentration in the range from 0.05 to 100 μg/L.The results showed that the phosphorus is fit the BBD to experimental levels of different variables and optimal conditions were established.A thread-based microfluidic channel device for separation was designed and used for fixed microfluidic thread-based,the angle of microfluidic thread-based can be adjusted by screws on the microfluidic channel device.The pretreatment methods and conditions of hydrophilic performance for thread fiber were investigated.The separation method,using the thread-based microfluidic separation device,was demonstrated through the successful separation of pigments in spinach leaves extract.A three-channel microfluidic device was designed in our lab,which was used to fix cotton-polyester microfluidic channels.The three-channel microfluidic device has been applied to speciation analysis of Cr(Ⅲ)and Cr(Ⅵ).The absorbance signal is linear with Cr(VI)concentration in the range of 0.8-10 mg/L,and the relative standard deviation(RSD)for 2 mg/L of Cr(Ⅵ)is 4.1%(n=9).This current work not only provides a new method for the speciation analysis of Cr(Ⅲ)and Cr(Ⅵ),but can also expand the application range of thread-based microfluidic device.