Studies On The New Microfluidic Paper-Based Analytical Method And Its Application

Microfluidic paper-based analytical methods have been emerging as an inexpensive, simple and portable analytical method in recent years. In this thesis, the microfluidic paper-based analytical method and its application were studied. Microfluidic paper-based analytical devices (μPADs) with different functions were designed and developed. A two-channel microfluidic paper-based analytical device was developed for determination of Hg2+, which realized automatic sample introduction. A three-dimensional (3D) microfluidic paper-based analytical device was fabricated and controlling the reaction time of every step in the assays was realized by utilizing manually folding the filter paper. Three-dimensional microfluidic paper-based analytical devices were developed based on "switch element" fabricated by polyester thread and folded hydrophobic paper; on-line filtration and controlling the reaction time of every step in the assays were realized and the devices have been used for determination of iodate and nitrite. The thesis mainly consists of five parts as follows.Chapter 1:ReviewThe characteristics, fabrication techniques, detection methods and application, as well as the recent progress of the related research at home and abroad of microfluidic paper-based analytical methods were reviewed. The topic of this thesis was proposed based on the review.Chapter 2:Two-channel microfluidic paper-based analytical method for determination of Hg (Ⅱ)A new two-channel microfluidic paper-based analytical device (μPAD) was developed in this paper. Automatic sample introduction was realized based on sample introduction strip to connect the sample solution and detection zone. The determination of Hg2+ was realized by spotting Ag NPs onto the detection zone based on the aggregation of Ag NPs in the presence of Hg2+. The two-channel determination was also realized by using two detection zones and sample introduction strips simultaneously. In addition, the device was integrally assembled in a miniature carton, which reduced the adversely influence of external environment on the detection during the determination process effectively. The device is simple and inexpensive, potable, and is well suitable for the detection of analyte in the real time especially in the field of remote areas and extremely resource-limited environments.Chapter 3:3D microfluidic paper-based analytical method for determination of ascorbic acid in the tabletsA three-dimensional (3D) microfluidic paper-based analytical device was developed. In the device, the reagents were immobilized on the device by using different methods. The effect between the reagents was avoided effectively, and the reaction time of every step in the assays was controlled by manually folding the filter paper in the μPADs. The device has been applied to the determination of ascorbic acid in the tablets with satisfactory results. The device has the advantages of simple fabrication, portability, low-cost, and rapid and sensitive determination, which is well suitable for the detection of AA in the tablets and other samples in the real time.Chapter 4:Studies on a new 3D microfluidic paper-based analytical method for rapid determinationA new three dimensional (3D) microfluidic paper-based analytical device was developed in the paper for on-line filtration and determination of iodate ion in table salt based on cotton-polyester thread as sample introduction channels, filtration zones, detection zones and "switch elements". The fabricating and the experimental conditions were discussed and optimized, respectively. Under optimum conditions, a linear relationship was obtained between the gray value and the concentration of iodate in the range of 5-250 μmol/L. The detection limit was 2.3 μmol/L. The proposed device has been applied to the determination of iodate in the real samples with satisfactory results.Chapter 5:3D microfluidic paper-based analytical method for determination of nitrite ion by controlling the reaction timeA new three-dimensional (3D) microfluidic paper-based analytical device (μPAD) was developed for simple and rapid determination of nitrite ion, based on cotton-polyester threads as sample introduction channels, utilizing the "switch element" to control the reaction time of every step in the assay. The stability of the device was improved by immobilizing sulfanilic acid and a-naphthylamine respectively on the filter paper. The fabricating conditions and the experimental conditions were also discussed and optimized. Under optimum conditions, a linear relationship was obtained between the gray value and the concentration of nitrite in the range of 10-400 μmol/L. The proposed device has been applied to the determination of nitrite in the water and soil samples with satisfactory results.