Application Of Paper-Based Analytical Devices In Sample Processing And Elemental Speciation Analysis

Paper-based analytical devices(PADs)are widely used in various real-time tests,such as medical diagnosis,environmental monitoring,and food quality control due to their simplicity,low-cost,convenient operation,and less sample usage.And after combining it with field amplified stacking(FAS),its detection sensitivity is also greatly improved.Previous research work generally used PADs as quantitative detection tools,ignoring the role of paper in PADs to filter sample impurities,and different field amplified stacking modes also have the role of screening ions of different electrical properties,so as to achieve sample purification and separation,especially for ions of the same element with different electrical properties,PADs based on the principle of FAS have the potential to be used as sample pretreatment in the process of speciation analysis.The application of this PADs-FAS to sample pretreatment,combined with other high-sensitivity and high-selectivity quantitative instruments,greatly simplifies the operation process and has far-reaching significance for the analysis of complex samples.The first chapter briefly described the importance of element speciation analysis,emphatically discussed the sample pretreatment methods and quantitative methods commonly used in speciation analysis,and summarizes the development history,manufacturing methods and applications in different aspects of paper-based analytical devices.The second chapter explored the application potential of the paper-based analysis device based on the principle of electrokinetic stacking in speciation analysis of heavy metal,especially Cr and Mn.Based on the principle of electrokinetic stacking in PADs,Cr(Ⅵ)and Cr(Ⅲ)can be separated according to their charged properties,and be measured directly after recovered,so as to achieve Cr speciation analysis without the aid of the subtraction.The separation and recovery of Cr(Ⅵ)and Cr(Ⅲ)in micro aqueous solution were characterized and optimized by spectrophotometry.The detection limits of Cr(Ⅵ)and Cr(Ⅲ)were 5.7μg·L1 and 8.6 μg·L-1,respectively,and the recoveries of standard addition were 88～108%and 90～110%,respectively.This method was combined with atomic spectroscopy(AAS and OES)to analyze the speciation of Cr(Ⅵ)/Cr(Ⅲ)in electroplating wastewater,and the results obtained by different methods were consistent.This sample pretreatment method based on PADs is convenient and fast.Moreover,combined with atomic spectroscopy,which is high selectivity but lack of ability of speciation analysis,this method will play an important role in the speciation analysis of Cr and similar multivalent metal elements.The third chapter explored the potential of paper-based analytical devices to purify complex samples and separate the heavy metal from serum.In this part of the work,we stored the serum samples in the way of dry blood spots,and then used PADs to purify and separate the chromium in the dried blood spot under the anion electrokinetic stacking mode.We optimized dried blood spots material,the dried time of dried blood spots,the leach time and the experimental migration time respectively in this work.Under optimal conditions,the sample recovery rate of Cr(Ⅵ)in serum can reach 100%,so paper-based analytical devices based on field amplification stacking also have great potential in purifying biological samples.